That's how I'm starting to look at this project, and there's nothing really wrong with that. I mean this is supposed to be a one-off, so I'm not worried about making extras. If you look at Ben Heck's first pinball, his was entirely cobbled. I mean he made his own cabinet, he made his own custom low res DMD display from a matrix grid of 5mm LED's, he made his own toys, his lockdown bar I believe is a cut up piece of aluminum angle. But he also used 24V flippers (which are very weak), and if you watch gameplay (or ever played it yourself) you'll see it's pretty hard to make some of the ramp shots because of it. Fact is the flippers he used were likely from an EM, and there wasn't a big demand for snappy shots back then, there were no ramps to get up.
One thing I've definitely noticed is that you realize how many fit issues you have. It's one thing to take existing parts that were all designed to fit together nicely because someone engineered them that way. It's a completely different story taking parts from multiple machines and merging them together. Let's take stock:
Stern early solid state trough / slings
New Williams off-the-shelf new flipper mechs. shooter rod, legs
Lockdown bar / lockdown mech from a 1978 Williams Disco fever
Coin door from a Data East LAH
1987 Williams F14 cabinet (bought all the hardware except the lockbar parts above and the side rails)
I did manage to lower the lockbar mech by creating a new hole, but that created a new problem (the carriage bolt stick in too far, so I'll have to trim that back with an angle grinder), as well as the bracket overlaps the bracket for the shooter rod by about a 1/4" that will need to get trimmed back. With the playfield in, the shooter rod now clears it, but it feels a little low (isn't quite centered on the ball), so I'll simply add some washers under the hanger brackets and it should all line up fine. Also by lowering it about 1/8" lower than it should be, I may have an issue with the lockdown bar engaging now. If that's the case, I'll simply widen the slot allowing it to line up.
Keep in mind it sounds like I'm really eyeballing a lot of this, and quite frankly I am (taking ruler measurements) which is way out of my style. I'm very much a "model it up in CAD and make sure everything lines up within half a millimeter" sort of a guy. But to model all this up for the sake of doing it, or documenting it just seems like a waste of time.
Whenever I finish this project and consider doing another one, I may seriously think about buying stock parts JUST in case the theme is desirable and boutique pinball building is still alive.
Tomorrow I should have my new 3d printed brackets, and I'll be "re-engineering" the lockbar mech. If I get all that done I can get everything back together. Oh I'm also painting a shooter rod bracket (the thing that prevents the ball from dropping through the playfield in the shooter lane) tonight that I stole from an extra high speed playfield I have. I'm pretty sure it'll mount just fine, I just have to think about how I want to do the art for the plunger position notches.