Duotherm vs. Suburban Replacements

[rasmuw]

I have a '67 Trade Wind that has a Duotherm 90020-812 B installed in place of the original Suburban NT-22 A. The Duotherm is rated at 20000 BTU input/16000 BTU output. My understanding of the original Suburban is that its input was 22500, with output of around 16750 (if I assume a 25% loss). I haven't used the Duotherm yet, and don't know if anything other than the fan is operational.

My first question is if the two units are fairly compatible--they seem to be. The second question is closely linked--will the Duotherm pump out enough heat?

There is a used Suburban NT 30 SP on Ebay right now that I've thought of bidding on. Is this a worthwhile switch? Is the Suburban set up so that the heat blows out left/right and exhaust is to the rear?

I won't buy a replacement if the Duotherm will put out enough heat (and hope it works) unless the Suburban is a big jump up in performance, ease of use, and reliability.

Thanks,
Wayne