Throttle body adapters from 4500 to 4150 style are they any good ?

[64duece]

You'll likely see a pretty small decrease in power when switching to the EFI from your carb'd setup. Negligable compared to what you'll gain in cold start and overall driveability. The 4150 TB should have better off idle manners than the 2000cfm 4500 flange unit. Most of them are progressive so, that helps abit. I'd bolt the 4500 on and atleast see how it responds before you adapt the 4150 on there.