well, if its a 2bbl car - there probably isnt much you can do other then try and get that factory 2bbl to work. I dont see the holley 2bbl working right for you and probably acting worse then what you have now. If you did decide to go electronics free in the carb you would need to swap the module and short harness for the 4 pin system and cut a slot open with a file to add the vaccum advance canister. That would bring the HEI to where it would need to be for regular carb use.
The 350 would work if you have the ability to get it tuned out right as well - but it would be just atrocious.............