Hello XXXXXXXXX
If the 91 sanoma has the 4.3 engine it will work in the 95 seira 350 because all the 4.3 is a 350 with 2 sylinders cut off of it. the trans should be a 700 r4 and actually all small block trans will fit up to either motor.
I'm glad to help and I'm here if you need anything else, just ask for toolpusher08.
If you feel like it's an acceptable answer click the green accept button that's how we here on the site get paid and your posative feed back score would be great!
THANKS!
Chevy Technician
ASE certified,expired. 30 years experiance self employed semi-retired.