ALLLLLLLLLLLLLLLL my cars with a Muncie(5), have a pure bone stock Chevy bell housing (both iron and alum) and good dowel pins on the rear of the block.
My 51 Chevy was the first car to get a Muncie (1968). I put it together with a 55-57 style bell housing. I absolutely DO NOT DISPUTE making the effort to align a bell housing. BUT, I have never had any issues with GM/Chevy parts for a manual transmission installation.
I have one Olds that is a FACTORY 5sp car (I ordered it new). The original small Olds V8 was replaced with an Olds 455 in 87, and the puny factory 5sp replaced with a Richmond Street 5sp, then the 455 was rebuilt to W30 specs in 2013. The bone stock Olds alum bell housing was used with the Richmond street 5sp tranny and it has performed flawlessly ever since.
So when it comes to bolting a bone stock Chevy bell housing to a Chevy engine and the bolting a manual tranny to the Chevy housing without taking the effort to index the engine/housing/tranny, I'm a believer.
Now, one exception to the above. My 23 T-bucket has a scattershield, which was on the car when I bought it several years ago. I have no clue if it was indexed. But the Muncie behind it works fine.
Have I just been lucky over the years? Maybe so, but if it ain't broke, I ain't fixin' it!
I have always used guide pins on the bellhousing to install the transmission. If the trans goes in with nothing more then a little wiggle of the output shaft to align the clutch splines, then I am good to go. Lakewood scatter shields can be a bit of a challenge sometimes, but not always. I do the same thing, if the trans does not just slide in on the guide pins, then I will dial in the bell housing (which really dislike doing and is a big giant pain in my opinion.) I will have to try one of those tools instead of dial indicator. Seems like an less frustrating method.
Well a little update , I started off tonight with replacing the bad bellhousing alignment dowel with a new Moroso dowel. The Moroso dowels were not the stock length but the longer dowels. I thought that I was receiving the stock length from the local auto store that I ordered them from but ended up with the longer dowels.
The readings became better but still not within tolerance. With nothing to lose I replaced the other pin as well hoping for a little luck that we would be in tolerance but we are still out. My last set of readings with two new pins are, 12 o clock 0 , 9 o clock 4 thousandths,
6 o clock 30 thousandths and 3 o clock 28 thousandths.
If I am understanding this correctly, I need a pack of 0.14 Offset pins to go in the 10 o clock position.