[MikeMoller]

Update - Found a set of 1.5 primary tube headers so installed them with 18 inches of 2.5 collector. Changed the converter to one with more stall and about 500 more flash. Leaned the carb up just a bit - from 69 jet down to 66 jets.
The result (in great air 30.4 barometer 495 adj alt) was best runs to date at legal weight (3470) - 9.152 and a 9.156, 73.0 and 72.99 mph in the eighth. Need to get this out to a test and tune since was doing this on race day, looks like on the right track. Car was running consistent 9.39 / 9.40 before at 70.2's mph.