OK so what I'm looking to do is build a custom b series transmission. My car is used on a circle track 1/3 mile. Right now in 2nd gear I run 8500rpm down the straights and in 3rd I'm at around 5500..I can't change tire size.

What I'm wondering about doing is switching some gears. I want to keep my current 2nd gear. Can I change out the 3rd gear for a longer 2nd gear. And change the 4th gear for a very short 3rd gear. And 5th gear for a long 3rd gear. Has anyone done this before. Would really like to know some input.

I race at a bunch of tracks so would like one trans to do it at at 1/4, 1/3, 3/8 and 1/2 mile tracks

2nd can't be used as 3rd. You can use a close ratio 3rd. 1.7xx is the shortest ratio available.

You can't use 5th for 3rd. The longest 4th you can use in conjunction with the shortest 3rd is the OEM 1.034.

I think I will just use this gear set I found last night should do what I want..
Gear-X B-Series Ultra Close Ratio Gear Set Race Kit 1

1st 3.07 [2nd OEM 2.105] 3rd 1.695 4th 1.385 5th 1.14

Might go with the m factory 3rd (1.652) 4th (1.385) and 5th (1.14) gears. But does anyone know if they use the stock hubs, sliders, and synchros? Can u literally just swap them out for the old gears or is there special stuff need to make them work.