Building a custom cb750 through the mail.

The craigslist here has a good deal about twice a year.

I bought a 1974 titled cb750k frame and 1978 750k engine for $150.

Scored an entire 1977 GL1000 front end for $150 shipped - trees, forks, rim, calipers, bearings, headlight mount, turn signals, axle

Thinking about buying old CB900F ($60) shocks to raise the back up a bit and make the bike taller.

Given that configuration what would be the ideal bolt in swing arm and rear rim solution to keep the bike as well balanced as possible? A drum brake with spokes is preferred.

Not knowing how much longer the 900 shocks are than the 750, I'd say the stock swinger and rear wheel meets all of your criteria quite well.

Are the GL forks longer than stock? Would recommend stock length shocks on the rear if it is close to stock length on the front. Taller rear + shorter or stock front will result in twitchy and potentially dangerous handling.

Drum brake on a CB750 is less than ideal on the roads with texting car drivers and other distractions. You need good brakes. Good drums on a small bike are OK but not ideal and on a large heavy bike, not a good idea.

Indeed ^ If you're going through the trouble to swap a bunch of parts, swap for something with a disc