You might not have to make such spacers. There is quite a bit of lattitude in the SPF's as to where the engine finally gets bolted down. They give you the opportunity to move the engine forwards, backwards, left, right, up, and such with their engine mount pedestals. Sometimes header fit and such dictate the engine's final resting place. See if you can move the engine back 1/2" in the chassis. I would never bolt the engine in place on a SPF until after I had the headers and sidepipes bolted up to the motor, they often dictate the need to move it a C.H. this way or that. In your case, the
oil pan may be the biggest interference item.