trans swap issue

i recently swapped the trans on my 91 civic si and everything was successful except i think this trans is for a diff car. i think this because my old trans i would be in fourth going 45 or so at like 2500 rpm. with this new trans im going like 70 in fourth at a comfortable 3000 rpm anyone know what trans this might be and from what car

If 5th gear is at 55mph at 2800-3000 rpms it's probably an Si tranny. If your rpms are lower, I'm guessing dx tranny.

DX, and hope to god it's not an Hf...

nah an hf tranny would be doing like 70 in 2nd gear at 6k maybe so im pretty sure its probably a si cause doing 70 in 4th is about 3500 or so.

DX probably. My DX was able to hit 110 mph in 4th, 5th is more of an overdrive gear than another gear. Because I could hit 110 in 4th, shift to 5th and will start slowing down before it would pick back up.