i have a chance to pick up a 77 nova 2door thats in goood shape for $200/500 but it has a 6 in it and i would want to do a 8. is this a hard thing to do. i work on cars and kind of know what im doing. do i have to chang the trns/shaft at the same time ??? and will the mtr mnts match up. and oh ya i just might have a 85 olds 307/4 brl that pprrrssss will that fit in