Thelovemachine

Hello, new member here. I bought a clean 1986 caprice classic 305 fleet vehicle from a church in 2011 when i was 17. It had 140k miles on it and ran well when i purchased it. I drove it for about 4 years until it started to run poorly and i couldnt afford to chase the issues or fuel it at the time and it has been sitting for about 7 years at my fathers property. About 3 months ago i went and checked it out and the interior was in great shape still minus a headliner, i put a battery in it and ticked the starter and it turned over no problem. So i started looking into fixing it up and have been looking into issues with it since. First off, i dropped the tank and steam cleaned it, no Rust! Then the right rear drum brake was froze up so i completely rebuilt the drums and put a new wheel cylinders in. I had problems with the computer controlled rochester twords the end of driving it so i picked up a used 1405 performer to put up top. Next id like to bypass the ecm and put a vacuum advance hei distributor with new plugs and wires in it and get rid of the computer controlled distributor, then check and simplify the vac system slightly, change the fuel filters try to start it. So first question any issues with bypassing the ecm and using a vac advance hei other then the inevitable check engine light? I have a running 1988 tbi 350 that has been converted to carb i got for free but plan on trying to get the 305 running first. Thanks for the help! I have more questions i will ask if i can get some help on the first questions i have asked.
-junior