How to get 400 hp out of 1971 340 .30 over

I think it will be interesting to see the sizing. I'm not sure if they get that flow rating by those sizes or if the are using a straight leg booster to get that flow number.
I'll ask them. I have been running 660's for the last few years, installed annular boosters, and a lot of jet changes to get them somewhat tuned for this altitude. I wanted something better without going to fi. I hope these are the ticket.