have a question about automatic transmission

[67camper_cruiser]

so my 67 got an engine swap about 2 months ago, (blok was completely done) maybe a 68 350 in it b4, i have now what i think is a 82 maybe 350...it ran like a champ specially up hill, now i go up and down the same hill every day with with it, only problem now is it does not get enough power when i accelerate, now when im going up the hill my petal is all the way down to the metal n im doing maybe about 60,, my engine is roaring like a beast and mph's keep getting lower as i climb... its deff not the same as before, also my swaped engine sounds great so i dont think its anything to do with that,,, before i would go up the hill like nothing, any suggestions...............also transmission was fine before to..