The top ten small blocks make interesting reading:
3 Chevrolets
3 Studebakers (eat your heart out, Ivor

)
2 Oldsmobiles
1 Pontiac
1 Plymouth
Or the top twenty
8 Chevrolets
3 Studebakers
2 Fords
2 Oldsmobiles
2 Pontaics
1 AMC
1 Dodge
1 Plymouth
What gets interesting with the big blocks is that, as time goes on and folk get better at, em, massaging their 'stockness', the engines that were designed as racing engines take over ... the 426 hemi and the Mark IV big block. The others put up valiant effort, MoPar RB blocks and the (very) occasional Buick, but its a racing engine show.
No Fords either, I guess because Boss 429 Mustangers don't want to or can't race. It would be nice to see at least one in there just for comparison sake.
The 'massaging' can be extreme. Extrude honed exhaust manifolds that are paper thin, and get binned after each event, etc, etc...
It is a shame Chris Leslie isn't on the board or well enough as he was very into this.
I think the closest the Buick-hemi thing got to being really 'stock' was Round 2, although, the hemi owner's (who flew down to Bowling Green in his Lear Jet) crew caused the Buick guys concern when they asked how much hp the Buick engine made on the dyno, considering it only had had its inlet manifold off the week before to make sure the cam was okay, and had never been out of the car its whole life.
In the Hot Rod article (above) you can tell that there is a whole lot of 'massaging' going on from the sidebars, and I don't believe for one minute that the Buick is 455ci.
All the best