Mike, you can try Langdons Stovebolt Engine Co. they make a hotwater heater plate for the 2 & 3 carb. manifolds. I think the kit was about $30.00 but try the link below.

http://www.stoveboltengineco.com/acartpro/category.asp?catcode=21

"If it ain't Steel it ain't Real"
"Earth the insane aslyum for the rest of the Universe"
41 1/2-ton, a work in progress
68 Shortbed stepside 327/325hp/700R4