Assuming "hold" means compatible, yes
Yes, assuming the TH350 has the Buick-Olds-Pontiac bolt pattern. A Chevy TH350 will also bolt up, but you will need an adapter from B&M or another supplier.
The bolt pattern on Chevy engines is unique. There are TH350 transmissions with both the Chevy bolt pattern and the BOP (Buick, Olds, Pontiac) pattern, but they are becoming somewhat rare.
Yes, in the transmission.
1986 - 1991.
Could be one of three V6 engines or a Chevy V8. The transmission won't bolt up to the Olds motor. However, you can change the motor mounts.....Use the ones for a Cutlass and a Buick, Olds, Pontiac transmission.
you can leave the transmission in or you can leave in the transmission
You can check the automatic transmission fluid on an Olds Alero by finding the check plug. It is located about half way down on the transmission. Loosen the plug and slowly pull it out.
Remove the u-joint from the back of the transmission. Remove the transmission mount bolts. Remove the transmission bolts. Remove the linkage. The transmission will slide backwards and can be removed.