For our "purposes" here, the orignal ratings of engines from the early '70s really have no significance. Add a mild cam to that 400 and will run away and hide from the Subaru. Those engines were MASSIVELY "detuned" for emmissions.
I get a lot of calls asking if we're "willing" to build a 400. HUH? In the last three weeks, I've had no less than 8 calls regarding this. The callers didn't mention names, and I didn't ask, but they all complained that the shops they were talking to ALL said "Just throw a stroker kit in it".
A 400 is a GREAT basis for a very powerful and durable engine. Scott Roberts' '68 Firebird went 11.10s over 118 with a fairly "mild" 406. Pump-gas street engine. In 1998... He put a "100 shot" to it and went 10.47 @ 121. The engine is still "alive" today. It has different heads and innards, as it now serves a different purpose, but the rods and pistons are still the same ones.
We're getting a block from up North Monday, for a "long rod" 400, making near 500 HP and revving hard past 6,500. Once he adds aluminum heads and a solid roller, a 7,000 RPM, 600 HP monster is "there" (future plans with modifications to the block "built in").
Vinny Madeya in SoCal just went 6.99 @ 199 a couple weeks ago, with a "stock block" 400 and a CAST 400 crank. 8,500 RPM, 15% nitro... (:-
GTO didn't get it's reputation from losing to SS396, and the vast majority were 389s and 400s.
Jim