engine mount locations

[guf]

i have a 71 and a 70 short bed. the 70 is the donor with a 350 /350 and the 71 has a 350/3 speed manual. the engines are both mounted in different locations. the 70 in front holes and the 71 in the rear holes. It is possible that they where both 6 cylinders at one time. when i move the engine and transmission to the receiving truck should they be in the rear mount location. (doesn't look like there is a hole on the front crossmember for the front frame holes). i searched the boards and seem to make my self more confused.
thanks

[71tahoe]

It's more possible that the 71 was a 6cyl at one time. 35+ years of grime can hide almost anything. Try scraping and poking where the V8 towers should mount in front of the 6cyl towers and you should find the holes. If they're really not there you could swap the crossmember from the 70 also.

Anyone know if this could be a 73 and up xmember?

[guf]

...and i also noticed that the bracket sizes are different. The smaller ones are the ones in the front location and the larger ones in the rear location...so yes there is front holes on the crossmember so i could use the towers from the 70 and move them to the 71's fron location?

[71tahoe]

The only reason I can think that the 6 cyl mounts would look larger is that they are longer from where they bolt at the top of the frame rail to the crossmember. If you're making an auto from the 71, you would need the V8 motor towers in the forward position and the driveshaft from the 70 to match. If you still have the crossmember that attaches to the manual trans bellhousing, you should remove it. I don't think the auto linkage will fit and it most likely will be in the way of the TH350.

Most of your driveline from the donor should bolt right up to the 71. The transmission crossmember might give you some problems but all the frames I have seen from different years had multiple holes predrilled. Everything should line up.

[guf]

thanks for the help I'm gonna head out and start!