I have a 1994 eg coupe that I want to swap a k 20 into. What is the best k20 to do?

 

That depends on who you ask... but a K20A2, K20Z1 or K20Z3 will be the likely choices.

 

Well I want to build like a 500-600hp boosted reliable daily driver with that being said… I plan on building lower end what are good internals that’s are not crazy expensive but good.? And how much head work should be done? Dont know much about k series I have a built d series in it now

 

Good parts aren't cheap... and cheap parts aren't good. Reliability costs money. You will have to be turbocharged for that level of power... and reliability is a "relative" term. Keeping the engine cool will likely be your biggest challenge.