I have been meaning to ask you what rear end is in the van???.Do you know the gear ratio??.Are they city gears in it??.That would mean the ratio would be in the higher range.I once built a Chevy side slide door cargo van and replaced the straight six with a oval track four barrel 327 sbc.It I guess was a 4.56 rear end gears.Hehe,we used to rock the throttle in first gear(to the floor and off real fast)and get the front wheels to almost come off the ground.