side-vented cast iron boilier

I’m having my boiler replaced, and I’m looking for something simple and reliable. The current boiler is a mod/con which is side-vented with Z-vent AL29-4C pipe. We have a chimney, but I’m relatively certain it is unlined (will confirm this wkd). So I’m looking for a cast-iron boiler that is capable of side venting. This seems to narrow the selection quite a bit. I’ve found the following models online:

Burnham ESC, Smith GVX, Weil-Mclain CGi, Utica SVB series 2, Peerless PSCII

Any thoughts on whether any of these stand out (good or bad), or if there is one I missed?

thanks!