Dirty dingos mounts

[Cheyenne350]

Currently working on a 78 short bed 2wheel drive with a ls1/4l60e equipped with dirty dingos engine sliding plates. My question is how far back did you guys go if your using these plates? My stock driveshaft fits well but I see from my yolk that I could go further back more, and on the plates I see little more room to play with so slide back. Thank you guys in advance... also added a picture of the passenger side plate