So, your biggest expense after the engine purchase is going to be exhaust. Your 2v accessories will bolt up (ac, power steering, maybe even alternator). The 4v uses all the same sensors as the 2v, but you may have to do some wire altering. I seem to recall the 4v coil packs are reverse polarity compared to the 2v, and I think you have to change the connector for the throttle position sensor. It’s not a hard swap at all.
EVERYTHING is harder with the 4v. way less room, parts cost more/are harder to find, double the cams, the coolant system is worse, and on top of that if you want serious power you need a power adder anyhow.
there have been many times i wish i started with a GT for all these little nickel and dime reasons.
my advice is use the wap block with a set of trick flow heads, enjoy the weight reduction, and similar power but there's no way in hell he's gonna do that now because of the sunk cost effect.
Iron block: 155lbs
dohc head weight: 130lbs (for both)
sohc head weight: 90lbs (for both)
WAP block: around 80 lbs
iron block sohc heads: 245bs
wap block with sohc heads: 170lbs (-75ish lbs!)
wap block with wap heads: 210lbs (-35lbs)
ever weigh the intakes? the huge cast aluminum 4v intake definitely weighs a LOT more than the PI GT intake. valve covers, cast aluminum on 4v's while sohcs are plastic, i think. oh and hood clearance is important, too.
just so people know, swapping an aluminum block into your car will shave like 95-100lbs off the front end. they may be all aluminum but its a LOT of aluminum
the 4v stock heads flow better but the trick flow head cam package will yield more power than a stock 4v. of course none of this matters all that much if you're going to throw a blower on it.
just so everyone knows the cost, pro's, and cons. if i could have it anyway i wanted i'd have an aluminum block with that trick flow head cam package. between that, the mm k member/control arms, and battery relocation you could easily shave 220 lbs off the front end of the car. that's gonna make everything better.