I plan on pulling my 454 mags next week. They are 1988 models bone stock 365 hp with 800 hours. They run smooth and one burns a quart every several hours. I have recieved several quotes from builders ranging from 3k-7k for rebuilds.

I thought about pulling them, stripping them down to the bare blocks. Having a machine shop install new rings, bearings, checking clearances, and installing a slightly hotter cam, and roller rockers like the 420Hp models. Then swapping the stock rochesters for 750 sea demons and better intakes. Installing some new valve springs, guides and seals. New hoses and oil coolers. I have installed cams, carbs, distributors etc on my own.

My questions are..
What work should I do on my own to save $$$$?

What cam/carb/?

What should I expect to pay per engine if I sent them the long blocks to freshen? I can dress the engines and install

Personally, I would go to Jasper for a STOCK rebuild on your 365 engines as they can do a very nice job for you in a close timeframe. They can do minor upgrades for a very small price increase.
If you are considering more than just a stock rebuild I'd go with the local reputable marine engine shop.