I put a FiTech Go Street EFI on the wife's '87 Olds Cutlass 442 last year. The engine is a 350 Olds V8 with a pretty lumpy cam. I'm very happy with the unit. It is very affordable and is self learning. I did have one small glitch, but a couple of simple taps on the touch screen to reset and change the camshaft selection the unit was up and running. I opted to use a in-tank fuel pump with a C5 Corvette filter/regulator to supply the correct pressure. You can do that or they have a Fuel Command Center that takes the fuel from your stock mechanical fuel pump to fill up the sump. Inside the sump is the hi pressure pump and regulator that feeds the EFI unit.
The car starts so much easier, no more choke to worry about and my mileage jumped about 4 mpg's. The more you drive it, the better it gets. It's a fairly simple system to hook up. You are going to have to ditch your computer controlled distributor for a stock non computer HEI or go with a MSD unit.
Plus there is a group on Facebook that is for FiTech EFI. It helps out people having any issues with the unit if they are having a problem.
Or you could go my route and rip everything out and stuff a Gen III or IV LS engine in your '81.
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GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.
3.54 Dana 44