I've done an A-Body & 5 1st Gen trucks with Mag engines
I can tell you exactly which fuel pump & line combo it takes to clear the correct Denso alt brackets I can post the pics of what you need to look for
I'm getting ready to Mag motor my 75' B-Body wagon
As far as the drivers side mount. Get one for a 340-360 & spend the Schumacher money somewhere else on your project
Put the Crosswinds intake on it & forget about it
Myron Pyotek? (A member here)can most likely enlighten you on hooking the 904 up to it & any balance questions
You can find him over in the racing section
Are you going to be using A/C?
