Thanks everyone for your help. With that information I did find an old post on here with same situation.
https://www.garagejournal.com/forum/threads/older-mr-heater-45-000-convert-lp-to-ng.453765/
The post confirms I need to order the 1751-024 Robertshaw kit.
AldeanFan I'll PM you...
Thanks Schoeny.... according the website they are the same (just more jets for the larger unit). My small 50K unit needs 3x jets. I think the 80K is 5 or 6 jets.
Hi All
I purchased a used Big Maxx 50K heater. Looking to see if someone has the NG to propane conversion kit they do not need. Usually a new store bought unit includes this.... and most don't need and toss in garbage.
If you happen to still have the orifices and spring I would like to...