The K&B .45 is an awesome engine - I know, I blew up dozens of 'em in competition when I was a kid. The connecting rod is probably the one-and only- weak point. There should be, I believe .003" clearance in both holes, top and bottom. This is the "optimum" number for glow engines at high rpm (approaching 30,000 rpm- this from I believe an RCM/MAN article some years back)
K&B is the only engine manufacturer that holds to this number.

I had two marine engines exceed this to the tunes of 32,900 and about 33,500 - used to kill one set of bearings and a glow plug per heat.

I shudder to think what I could have done if ceramics were readily available and affordable back then...

If you can still get them, spend the money and get an "RPM" connecting rod. This is your best investment.
A good tuned pipe makes these engines killers....