Adapt, adopt, improvise and overcome. Be flexible. Most R/C puzzlers have multiple solutions. In a nylon engine mount you can use self-tapping or machine screws in place of bolts. You can tap the holes in aluminum mounts and use bolts (and adding nuts to the exposed portion is a real belts-and-suspenders arrangement). Engine mounts, in fact, are a recent innovation. Build a wood mount out of plywood and maple frames. No law against it.

Don't believe R/C is limited to R/C products. Hardware is hardware.

For linkages a simple "Z" bend is often the best solution. And by far the least expensive.

On this blessed modern Internet it is possible to download .pdf files for a lot of the (few) available kits. If you get stumped you can check them out for solutions that may not have occurred to you. Same for reading old R/C Magazines to pick up novel solutions to the same old problems.

Be thankful. I have some old Air Trails magazines with tips on making propellers. At least those are usualy vailable . . . except in the specific size you want that day.