I installed a Spectra gas tank in my 50 after searching this forum.

Check out this thread
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=595485&page=1

https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=595485

If you order from a classic or others you may want to ask if the tank is overseas made, if the bottom threads are metric, and if the fill lines match. The problems discussed in that thread may have been corrected by now.

Spectra was available from Rock Auto, and Orielly auto.

Good Luck