I am running one of the old Mega Squirt3 kits. Keep in mind a lot of technology has passed under bridge now on EFI. When I built mine my limiting factor was a intake manifold to support HP. And it was a 440. Not a lot of support in any arena. Had to fabricate many parts by hand and don’t tell anyone but am running Vette coils. Jump forward to 2020 I think Holley has the advantage over all. I would not purchase MS lots of changes there with regard to support, quality etc. in fact I am doing it again right now on a build for a 72 Demon. All Holley. Their tech support and RnD is top notch my opinion. Keep in mind asking carb or EFI is like asking this bunch which cam is best! Hah! Welcome to the site and make no mistake this mobs taste on wine women and song is as varied and eclectic as their taste in cars. The common denominator is a thirst for knowledge. Heck sometimes we even talk about cars!