5.3L GenIII /TH400 swap

[68fleetsidec20]

The 350 in my truck was on its last legs; the heads were cracked, valve seals leaking, cylinders heavily worn and pitted and it failed the emissions test misserably, so it was time for something new.
I picked up an almost complete 5.3L for around the cost of a low milage sbc. I decide to keep the TH400 as with my 30" tall tires and 3.08 gears I wouldn't be needing overdrive, although torque converter lockup would be nice.
Two days I pulled apart the front end of the truck and pulled out the tired 350

Yesterday I finished preping the engine and bolted it to the transmission using a spacer GM12563532 and new longer bolts GM12563533. The spacer and bolts are to make up for the shorter torque converter of the TH400. I had heard that the flexplate had bolt holes that would match up with the th400 torque converter, however I did not find this to be the case. Using the extra raised pads on the flexplate I carefully drilled holes to mount up with my torque converter. This seemed to work good.


I was then able to drop the engine in keeping the transmission in its stock location so that the shifter linkage and driveshaft would be uneffected. For the motor mounts I used common adaptor brackets and swaped the original trucks pedestle mounts side to side and 2 of the 3 bolt holes lined right up. The third one I will drill.
I test fitted the factor 5.3L exhaust manifolds and the drivers side fit with minor modification.

and the passanges side with a little more modification. The frame will need to be slightly clearanced as well. However If I not mistaken the 67's have wider frame rails around the engine then the 68-72s so it may not be an issue with other trucks.

The heat shields caused problems on both sides so I will leave them off for now, but the should fit with some modification.
I'll keep this thread updated with my progress, the plan is to have it finished by the end of the week.