I am installing a newly rebuilt 3rd arm in a 54 passenger car. I noted that there are special bolts specified for attaching the assembly to the chassis. The parts book identifies the bolts as part number 217208 with an asterisk. In the footnotes the asterisk denotes a bolt made of "special steel". Am I wrong to interpret this as a grade 8 bolt or would it be a bolt of an entirely different metallurgy? What say you Gene?

I woud feel safe with a grade 8. IF I REMMBER CORRECTLY THE ORIGINAL BOLT HAD A LOWER HEAD..

I agree with Gene. A Grade 8 bolt will be more than adequate.

In the time period when these classic cars were designed and manufactured most hardware was not heat treated. Special bolts were made of medium carbon steel and heat treated to perform similar to what we now call Grade 5. There might have been a few situations where they were heat treated to Grade 8 strength.

If the joint uses washers and nuts make sure you get matching Grade 8 hardware.

If the shop manual has a torque value for that joint use that value. You could damage the mating parts if you create too much clamp force.

Thanks to both Gene and Rusty. I'll follow your advice and I will also check to see if there is any difference in the hight of the bolt heads between the ones I removed and a grade 8 replacement. Hopefully the the ones I removed were originally the car.

Just use grade 8 the large bolt under the engine is a @itch to get at and replace use the old one because it is very short and would be hard to duplicate,I believe.