My car has the early type trans mounting points, the later type is easier.
If it was me I would keep it a manual trans with the V8.
1971 and later Muncie 4 speeds and B&W super T10's have the speedo cable output on the passenger side which is better for mounting a torque arm bracket.
The motor mounts will determine the trans location front to rear and side to side.
You want the radiator and the front of the block parallel to each other and the trans pan parallel with the rocker panels.
What headers are you going to use ?
Long tube headers will help determine the height of the trans mount, while short tubes offer more flexibility and ground clearance.
Some people will make a dropped crossmember instead of using a BFH to reshape the firewall+trans tunnel for clearance and driveline angle.
A stock crossmember may act as a shelf to hold up the 400 while you get the engine in place and the headers on.
This is the Hooker TH400 mount for later Vega/Monza, not too complex.
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Stock crossmember with a TH350 trans and a fabbed torque arm bracket.
Transmission%20and%20torque%20arm%20installed.jpg
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