going backwards need header advice

[pkj]

i am going about this project backwards and i need some help so it will all fit in the end. the truck is a 68 long fleet 307/3 speed.everything is stock. in about a year i will install a 400 sb with vortec heads, but i want to do my exhaust now. also later i will lower the truck 3/5. so nowing the future engine what header (coated) thru summit will work best for money. engine will be mild. torque being the #1 priorty, trans will be 5 or 6 speed manuel. since i am intreasted in torque what length header will be best. pipes will be 2 1/2 inch regular bends, H pipe, welded mufflers (not flowmaster) tailpipes exit at rear. i know the 307 will suffer some from this combo, but i want it to be tops for the 400. will the 307 header work on the 98 & up truck vortec head? what are best gaskets and bolts to use? i will advise exhaust shop of lowering and they should be abel to accomodate future lowering.thanks for all ideas and advice.