Classic & Vintage - need answers about upgrading my old raleigh

So this is the story... I bought a raleigh triumph a few months ago to see if I would actually like riding. Turns out I love it and want to upgrade, the only problem is that it seems like any new parts aren't compatible. My main concerns would be with the wheel set. I bought a set but the guy at my lbs told me that they wouldn't work on my bike although I feel like they would. I would need to put a cassette on the new wheel set. So I took his advise and got a new freewheel and chain for the old wheels. The originals are awfully heavy and I have just learned the hard way that they are near impossible for braking in the rain.
Also, I want to change the crankset. Again, I'm not sure if newer cranksets are compatible. Other than that it seems like new brakes are not going to work because the bolts are wider than the brake mounts on the frame. Sorry if it seems like I'm rambling but I would love to put this new wheel set on. And I hate to admit defeat. Please help.

If your bottom bracket cups have 24 threads per inch, you are in luck. because this is consistent with the current international standard. If you have the older English 26TPI, you may be able to force fit an aluminum Swiss cupset (25.4TPI), but these tend to be rare and expensive.

If you have enough metal around the brake mounting holes in your fork crown and brake bridge, why not just ream them out to the newer standard? Also, note that it will be easiest to use brakes with standard external nuts, rather than the modern recessed system.

You can update to newer wheels, but you will most likely have to spread your rear triangle, which is pretty easy with a steel frame.

Cheaper to find a bike set up the way you want. Building up a bike is best suited for those of us that have a pile of surplus parts laying around.

You say you bought a set of wheels. What did you buy? we can most likely help you make em work.

As for the brakes, just look on ebay for a pair that uses the external nuts, or if you have centerpull calipers like these http://velo-orange.com/diaco750cebr.html you can swap out the bolt on the front caliper for a non-recessed one. like this http://cgi.ebay.com/Weinmann-Early-Vainqueur-999-Brake-Part-Bolt--NOS!-Frnt_W0QQcmdZViewItemQQimsfpZTL090621148001r24034QQimsxZ20090621QQitemZ270412586299QQsalenotsupporte d

wrk101 -
"Cheaper to find a bike set up the way you want. Building up a bike is best suited for those of us that have a pile of surplus parts laying around."

Good advise.

You can use the other bike as an alternate.

the wheels I bought are just a pair of alex akx1.0 nothing great but far better than the originals. They fit onto the frame and the brakes line up. But I'm not sure if my chain would be compatible with both the old crankset and new cassette. I guess it should since I put a new freewheel on it. Buying a new bike would be nice but I just don't have the money to drop all at once. Plus, I like the idea of building one up and doing the work myself.

Back in the day we used to convert these bikes to 3 piece alloy cranks by using the original cups and the new spindle with loose ball bearings. The other option is to have the BB taped from 26tpi to 24tpi..