Tranny swap

[68GMC454]

when i got my 84 gmc 454 granny tranny i wanted to switch it out for a 5 spd out of a late 80's truck. i think that was abotu when the 3/4 to 1 ton trucks got them. now the ol ladys brother owns a tranny shop, and another one works in one. they said and i forget exactly why, but wont work with my 454 from my 84.. i still want a 5 spd, may have to call advanced adapters or somethign like that to get somethign to make it work. if you do let me know, i have acces to the pedals and stuff, just need a tranny..