How do I determine if a particular crankset and BB combo will fit my frame?

In question is a 200mm crankset (intended for a KHS 747) with outside English threaded BB and a MTB that came with a 68x113 BB.

Is there a way of bolting these two together? The bike doesn't get used as an MTB and the extra ground clearance should accommodate the extra crank length.

68x113 is English threaded. Sounds like that part of it is OK. Sometimes there are clearance issues with road rings on mtb, but that's another thing.

Maybe, probably not, you really need to put it together.

The spec your quoting isn't normal bike talk, 'outside English threaded' isn't a standard description for a part, from a quick google search, what it looks like is an external BB, i.e. HT2 or a variant of this, this will fit your frame (the 68mm is key here, as road cranks are designed for 68mm, not an MTB standard 73mm BB shell), the bigger/deciding issue, is, will the 34t inner chainring contact the chainstays, until you have fitted it, it's impossible to know. With an external BB, you aren't able to adjust the chainline as you are with a tapered crank, so it's a will or won't result.

OK that's helpful. Just to confirm....So the outside cups will thread on but the chain rings may not line up and/ or clear the chain stays.
Is that correct?

What about the crank axle, will it maybe not be long enough to accommodate the width of the BB?

I'm thinking of just running a 1x10 setup as well.