How do the V6 headers fit ?
I would position the motor where the headers fit best, then make or modify the motor mounts,oil pan and trans crossmember as needed.
For the bellhousing use a V8 Monza setup, it uses a 10.5" clutch and the same cable type fork as your Vega but it bolts to a 4.3 V6 or a small block Chevy V8.
this allows you to reuse the stock Vega clutch pedal and cable linkage.
Truck bellhousings usually use 11" clutches so they take up more room at the firewall and the do not use the cable fork linkage.
Most Vega engine swaps will require some firewall massaging with a large hammer for bellhousing area.
zerks can be removed after greasing or newer style inner tie rods have the zerks facing the rear of the car instead of towards the oil pan if you are replacing them.
after you clearance the firewall jack up the trans tailshaft as far as possible and recheck the oil pan clearance, you may still need a modified steel pan.
https://kevkoracing.com/collections/4-3 ... -3l-v6-pan Kevco Racing makes 4.3 pans for one or two piece rear main seal blocks but you would have to call them for a V6 Vega pan.
It looks like the engine needs to go back
have you tried the mounts with the trans and bellhousing removed ?
and there are 2 different heights for factory rubber mounts on a 4.3