I want to radial lace an old eighties aluminum wheel to be used as front wheel for my ss project. (no front brake)
But I noticed that the nipple holes are slanted backwards and forwards. Can I get away with this?

Mine just have a little offset right or left depending on which Hub flange the spoke is to go in

I have no clue about your backwards-forwards issue ..

submit pictures .. that may help clarify things..

What about the hub? Not all hubs will support radial lacing.

Nipple holes slanted backward and forward are very rare. A few companies experimented with the concept at one time or another, but the idea never took hold because it introduced more headaches than it solved. IME, unless you have wooden or filled rims where the nipple is supported by the sides of a deep hole, odds are that the rim was drilled radially (except side to side).

Even if the rim is drilled forward and back you might still build radially. Use a hub or ring and 4 spokes to lace at 4 positions 90° apart and tighten slightly (not enough to overly flex the rim. Check to see if the nipples swing into the line of the spoke, or resist and set at an angle with a bend where the spoke enters. The former is fine to build radially, the latter argues against depending on degree.

To clarify; The holes are drilled offset for the left and right flange and slanted so that when you insert a nipple it points in the spoke direction for a 3 cross lace pattern.
The hub I want to use is a high flange Shimano item form the early eighties. I don't expect to run into problems using it with a radial spoke pattern. But you never know

Rim brakes are fine with radial lacing. The problems with radial lacing occur with hub based power or braking (rear wheels & disc brakes).

Assuming you're not using sockets and eyelets, and a thin aluminum rim, then It might not take much to straighten any slanted holes using a drill (and probably using nipple washers to even out the pressure).

As mentioned, most of the 70's and 80's era hubs weren't designed for radial lacing, and you can pull the flange off.

You assumed right, these are simple aluminum rims without eyelets. Drilling out the holes a bit, to get the nipple to seat better, crossed my mind but I"m not sure if removing any material would be a good idea. Perhaps the aluminum will form around the nipples when tensioning up the spokes. But on the other hand this reforming process could take a long time and the spokes might loose tension over and over again. Or if the aluminum is brittle the nipple holes might crack open.
You make a good point about the high flanged hub. They have holes in the sides so a radial spoke pattern will put extra load on them. It would have been better if the flanges were solid.

Maybe I should give up in the idea of radial lacing.....

You're overthinking this.

First of all, as I said earlier, forward/back (crossed) drilling is rare, and IME was never done with simple single wall rims. There was an exception to this, and it's easily recognized by formed "pods" for each nipple, and drilled forward back (only some).

If this is a used rim, you might be seeing the results of the seating on the prior build. In any case, nipples are free to rock a few degrees in the spoke holes, and unless the hole is very tight, they'll come into line when built (see the test I suggested earlier).

As for radial stress on the flange, the flange size or "kidneys" cut into it aren't the issue. The negative effect of radial lacing occurs entirely between the spoke hole and outer edge of the flange (regardless of flange size). While it may void a warranty, radial lacing rarely damages flanges except if over tensioned, or with hard use and stout spokes (ie. 2.0 plain gauge).

Build this with butted spokes and you should be fine

I wouldn't do it unless Shimano explicitly rated the hub for radial lacing. What benefit do you hope to gain with radial lacing?

Note that all the cracked hubs in JT's photos are laced with 2mm plain gauge spokes.

Of course, it's strictly the OP's call. His hub, his rim, his dough.

. . . his neck

Not a major concern, not because I don't care, but because the consequences of the unlikely failure aren't likely to include a crash. Of course the rider may have a long walk home, but that's not a safety issue.

Good to know.

yet still, the question remains: "what benefit do you hope to gain with radial lacing?"

Sometimes it's only a matter of "because I can". For some it might be "because people say I can't".

i'm embarrassed to say that i resemble the remark. but not with regard to radial lacing.

Well, for the same gauge and number of spokes, heads-in radial do get a bit stiffer than cross laces.

And a tiny bit lighter.

And heads-out, with different color spokes/hubs can be look quite nice.

So, if you aren't troubled by flanges breaking or nipples unscrewing, or the old claim or harsher ride, I think there are some decent, if not overwhelming reasons for using radial fronts.

Other than the cool factor and the experience of building my first radial laced wheel, none.

I must say those broken hubs look rather worrisome. But they won't cause a near fatal crash so I'm willing to risk it. Other than some spokes it won't cost me much I do fail to see how double butted spokes might prevent these failures. Do they stretch easier therefor preventing the flange failure?

Pretty much. FB covers it fairly well in an earlier post.

Without getting into details, think about bungee jumping. Would you jump off a bridge using a nice solid rope instead of a bungee? Think about why, and the same logic applies to spoke selection in wheel building.