I agree with you on the con rod it does look kinda week in the savage motor, actually the quality is pretty low on this motor compared to the marine engine we use and that will be were it fails.

The Nova Rossi line for cars is very high quality rod included and they also make the best .21 size marine engine in the world.
Remember this was a question of high nitro use in general and I know for a fact that the Nova Rossi line of car engines love high nitro.

As for head clearance I make my own heads for my boats and I run them as tight as possible until I see sighns of detination then I will raise it a couple thousands.
The Savage is stock and I never bothered to measure it because there was no sghn of detonation either and the truck is just for fun.