This may be "much ado about nuthin'", but I'm still going to ask. I'm replacing the original "Eagle by ARP" 8740 rod bolts in my Eagle (naturally) rods during this rebuild. The replacements are ARPs of the same length and 8740 material, but not the "Eagle by ARP" series, and appear different in a couple of ways:
1. Less total threaded length (same overall length, but threaded section is approx. .050" shorter)
2. Narrower shank by .015" (.360" vs. .375"); also longer due to shorter threaded section noted above
3. The new bolts are also lighter, enough that when I recalc'd the bob weight it worked out close to 20 grams lighter

Considering the point of this swap is simply to put some new bolts in previously "touched up" used rods, are the differences between the old and new bolts liable to throw something off dimensionally due to differences in how the two styles of bolts react when torqued?

FWIW, the old bolts were installed at 63#s, since I didn't have a stretch gauge at that time. IIRC, the recommended stretch should be around .006", but I don't know how close that comes to matching that particular torque rating.

I'm not worried about the bob weight differences, just the potential for the rods not being round when the new bolts are installed.