Dang....bypass shocks are nice. Even if they allowed it back then....too rich for my blood. Even with being part of team sponsored by sway-away....  I would agree tho....good suspension will help keep you moving faster.  Engines don't put out much more than 100-120hp....57-60 stock.  I've got a good tranny builder.... couldn't tell what internal parts would cost. 3Rd & 4th start at 100 a piece for custom ratios.
1&2 are quite a bit more due to It's construction. Ring n pinion....you can drop coin there too....or stick with good stock units. Hell....you can even get away with some that not broken but not good enough for street rebuild as they would make noises....in an off-road race car....should work fine.

There's lots of opinions on shock set up(Some prefer the spring/torsion to just support weight of vehicle and rely on shocks to handle all of dampening....others a combo of both)....gear ratios. it'll take test n tune days to dial stuff in. all part of the fun. Must be fun.....BR is still suffering the effects of being bit by the vw beetle bug..... just like me...