Both are in 7000# + mud trucks. One truck has 50" tractor tires and the other has 44" boggers. They pull very good to 7800 rpm. I should of mentioned, it takes atleast 1.875 header tube to cover the exhaust port. I had a 406 very simular to these two with B T1 (drag s10) and the canfield makes more power.

canfield 23600
 

i ran these heads on a 406 and a super victor the heads and intake where both ported w/13.1 comp powerglide 4.88 gears 32" tires in a nova that weighed 3000 with me best et was 9.87 w/1.30 60'. the only problem i have with these heads is if you have a lot of lift this offset will wear roller tip into alum. rocker body any you will need to replace intake rockers about every 300 or so runs,i need a shaft system is what canfield said for that much lift. my lift was 739 bobs is 728 both from cammotion. check out profile ( bobtemplin ) its a 406 i built with these heads it weight is also about 3000'- best et was 9.98 best 60' was 1.30 with t/350 trans my profile is ( nova72990 ) look at gallery my old blue nova with the 406