Since this is the street rod section, most of the info here probably applies more towards the guys building the pre 60s stuff, not whatever applied for the 60s and newer stuff.

For what its worth, my 39 Dodge pickup that is on a 91 Dakota frame has the spool motor mounts on its 5.9 Magnum (360). The biggest difference is that the motor sits back 6" from the original motor location on the frame. I did not (nor do I ever) expect anything the Mopar factory ever offered to "fit" perfectly for my application, but it was nice to be able to modify some parts off Mopar vehicles to make the process work more easily. I try hard to keep the brackets that bolt to the motor unmolested.

I have built a few street/hot rods (more then a dozen), and in every instance, the desired motor and trans were hung in the engine bay on the cherry picker with the trans supported with a floor jack. They were positioned where they needed to be (sometimes there is very little clearance, the motor/trans has to sit in an exact position) and then brackets were built to hold the motor/trans in that exact position. I find its often easier to locate the trans mount before building the motor mounts. The option of being able to use a factory engine bracket and part of its existing chassis bracket to locate a motor/trans is a nice advantage.

Sometimes the biscuit motor mount is the best option because it will fit in places the spool mount doesn't fit. When I use the biscuit mount, I usually cut off the stud and drill a 3/8" hole through both steel brackets and the rubber and insert a 3/8" bolt with a lock nut. That still allows motor movement without the concern of easily breaking the rubber mount that sure seems to be a lot weaker these days then they used to be. Gene