I have a 1969 Olds TH350 and need the bolt thread size for the converter inspection/dust cover.

Thanks!

 

Those holes get completely hammered over the years. They're supposed to be 1/4"-20. But I've had transmission that had 5/16" sheet metal screws shoved in there.
You'll have to see just how bad the holes are, and they might need rethreading and/or helicoil.
Note that most inspection covers, especially the aftermarket ones, have terrible fitment. Don't be surprised if it makes all kinds of noise when you fire it up. It usually takes me three tries or so. Install cover, start it, remove cover, cut away plastic, repeat. OE ones are better, but no guarantees.

 

Makes sense. I will probably go with the 1/4-20 helicoil suggestion.

Thanks!