Replace this bolt?
 

Should I replace this bolt? My starter died and I have a good junkyard replacement (bench tested at an autoparts store). Is this bolt too far gone to hold the 32 ftlbs of torque it will need? It looks like three threads are good and clean going into the transmission bell housing. But a couple are flattened, as you can see in these low res photos. Why are a couple flattened? How does that happen?

https://ecomodder.com/forum/attachme...1&d=1548123569

https://ecomodder.com/forum/attachme...1&d=1548123594

https://ecomodder.com/forum/attachme...1&d=1548123606

It doesn't look that bad but that's pictures for you.
If there is any doubt replace it with one as least the same strength rating.
A metric starter bold is probably 10.8 rated. Don't replace it wian 8.8 because it will snap.

If it threads in easily then I suppose I'd use it. Anything other than the smallest binding and I'd chase the threads in the block and the bolt and/or replace it.

I learned this the hard way. Swapping a car from rear drum to discs once, I cheaped out on the mounting bolts since they were missing from the (used) calipers I bought. Of course, one snapped putting them in. Won't do that again.

I'm with the others. Looks good enough to me. As long as it doesn't bind like Frank said.

I’d use it unless it binds up on its way in... the head studs got nicked up as I lifted the head off my LSJ and I used them over (ARP is reusable though) and was fine

Would any of you use anti-sieze on the bolt, or something similar? I imagine a danger would be that the bolt backs out on it's own. I worked on removing the second, lower starter mounting bolt, which is longer and I think extends through bell housing into the block. It is also fighting me. I hit it with PB Blaster and removed some stuff for room. With a cheater bar I get slight movement, but I am worried maybe the bolt head is breaking off. Ugh. I expected this little job to be simple! Now I feel like the car is off the road for a while.

I probably would. I've never had a problem with anti-seized fasteners backing out.

That's good. I just tested the bolt in the whole again and it does bind up after awhile. Pretty badly too. I'm wondering now if maybe when I did the transmission swap, if maybe I didn't clean out the whole is well enough. I was much newer at all of this back then. Maybe I really screwed up without realizing it until now. We'll see!

broke the bolt in the block
 

Gave it some more PB Blaster and went in as gently as I could to try and remove the bolts but it broke. This is the long lower Bolt because through the starter mount through the transmission bellhousing and into the engine block. At least I know now why my starter wasn't working anymore. The gear teeth raw shredded. It did a little damage to the flywheel too.

https://ecomodder.com/forum/attachme...1&d=1548203008

I'm looking up videos for removing the broken part of that Bolts from the engine block, and because of how awkwardly placed it is if I can even get the bolt out at all I'll need to pull the engine out of the car.

Here comes fun! Eric the Car Guy to the rescue?
https://m.youtube.com/watch?v=c-VD1yx61bA