Maybe I've learned a good lesson . . .

junkyardhero said
if you consider that it's probably turning 200lb + of stuff after the trans it's not all that crazy. wheels, tires, brake drums, driveshaft, axle... it's the old race car saying: ounces add up to pounds.

That gets back to how effective are dynos in replicating the low rpm loads?
If the chassis dyno is anything close to repeatable, then below intestate speeds, the van was less torquey and less responsive at full throttle with the ported heads, cam, and 4 bbl than it had been as a 2 bbl. The saving grace is part throttle kickdown of the transmission.