[Rich Biebel]

Sold bronze will work in iron heads but they need a little more clearance on the exhaust side.
I have seen many places not use seals also to let a little more oil in there on that side.

After I thought about it the guide that seized on my tow vehicle was a screw-in bronze.....Only one to ever do that in my memory...

I like the thin walls the best....honed to fit with a Sunnen hand hone....