I love building my own stuff and rarely pay anyone to do anything for me unless I don't have the equipment to do it. I would rather go buy the equipment than pay someone to do a job for me.
Welcome, Phil. I'm with you on the do-it-yourself approach, that's how I ended up with my wire feed welder, my TIG welder, my paint booth, my machine tools, and on and on...
Stock bore on a 390 is 4.05". If yours is really 4.135", someone has already bored it way out. Most 390 blocks won't take more than an overbore of 0.060" without the cylinders getting real thin, so the first thing I'd do is have the block sonic checked to see what the wall thicknesses are. You don't want to see wall thicknesses below 0.125". If you do, you should consider acquiring a different block to start with.
There are some 390 blocks that will take a big overbore, so again you will find out what you have with a sonic check. You may also have lucked into a 428 block there, which has a factory bore of 4.13". If that turns out to be the case, congratulations! 428 blocks can be hard to find.
I'm afraid I won't be much help on the flywheel/starter/bell questions, since I've always used the later stuff, but I'm sure someone here will chime in with the information you need. By the way, post some pictures of your car when you get a chance...
Edit - Oops, sorry, I didn't see that the block you were starting with was a 428. My bad...