[BruceWilkie]

If its going in a 400 in a 68 CAT none of the 3 are a good choice unless all your interested in is sound effects. Cam for a 400 vs 455 are totaly different character. Stroke difference is main reason why. In fact if I still had my 68 Cat I'd run either the Summit 2800 or Edelbrock "Performer" (depending on compression). Especially with street/highway gears. The 2800 pulls from idle to about 3800(like a freight train) where it levels off to about 4500 (then falls like a rock).
HOWEVER my old 68 bird convert(heavy but not quite as heavy as a Cat) with 2.56 gear out-pulled my freinds 4.10 geared 4 spd 355 SBC 70 Camaro that ran low low 13's in same trim. We never got my car to the track but plenty of deserted highway "tests" left him swearing there was no way it was a 400. I had small tube headers and an RPM intake/thermoquad.

[shoebox1.1]

my combo is more than likely be 455, 10-1Cr 6x-4's fully ported,2802, 72 intake, 800qjet, long branch manifolds 2.5 to tail, 2200 ish stall 3.23 posi. look stock front to back (428 ho cat) and runs whatever it runs! lol my buddy had this same combo in a formula with no porting,log manifolds at 3900 race weight and was consistant 7.70's in the 1/8th mile.

IM NOT GOING TO USE THE XE274 just curious what cars run well with it. i hear about a lot that dont!