I have made email contact with Alain. Sent him lots of info in the CPP Saginaw and Toyota options. His early 265 front motor mounts present a few challenges for pulley compatibility and pump mounting. As Ed said: The Saginaw (which I've done several times) is outside the frame rail for added header/etc. clearance. The Toyota is mounted inside. The Toyota seems easier to install. No welding, No drilling, no moving of the shock mounts, as far as I can tell.
CPP has a special pump/motor mount kit for the early front mount (bird leg) SBC and they have the crank pulley. Crank may need to be drilled and tapped. Seems like Hot Rod Jerry has some kind of jig fixture/drill guide for that..... and instruction.
For those thinking of doing power steering, there are three phases of work to be done after the desired box is chosen.
1. Box mounting
2. Column mod or new column. Possible intermediate shaft and Ujoint needed.
3. Pump mount
None of this work is difficult, lots of instruction and all in "kit form". The con is the price. I recommend CPP over POL. The CPP kits are sold by many vendors. There is/was confusion on the POL Saginaw kit because the kit says 47-59. I have helped several people with the POL kit. The POL kit, at the time I was involved, DID NOT realize that there needed to be two different hole drilling instructions. The frame on AD is 5 1/2" tall and the TF is 6" tall. One hole "fell off" the frame.
The CPP kit has two drilling instructions for Saginaw box mounting.
Be advised that parts are scarce, kits on back order, parts on back order. The cupboards are bare in America right now. Chances are you will wait for a long time for delivery and the prices of everything are going up. So pull the trigger now if you can. The excuse is Covid, not sure about that. Could be China choking us off for a while to see how we like it. Many things are automated and don't need a lot of workers. People working from home just fine. I guess transportation is the bottle neck and raw material.