Eric, there was no cutting or welding involved with the install I did... as far as bolting up the Griggs unit, there is one locator hole that is a perfect circle, and the other three are oblong, allowing for some movement.
GT_90, I
had to set my motor back the 1" allowed by the mounts on the k-member because the drain plug in the rear sump of my Moroso T-sump pan was right up against the tube that runs from side to side (sits in between the two sumps in other words). I was very unhappy about the plug not missing in the stock location, but at the same time, I was glad the k-member had that option already built into it. So, in a strange way, the setback did help a bunch... I could drain the oil from my rear sump, lol.
It's been said that the engine setback helps weight transfer, exhibits better handling, etc.
Oh, I had to have my alum. driveshaft shortened 1" as well, and had to do some modifications to the x-member. That's about it for mod's, in my case anyhow, to allow the engine setback.