I got them from Rick at Sunbeam Specalties in California. Cost was $255. plus shipping. Quality seems OK but I have quite ALOT of deburing /cleaning to do on the flange inlets.
They only come un-coated so after I get them test fitted & make all the necessary reliefs in the tubing to clear the motor mounts, starter, etc... I'm going to send them to Jet-Hot with another check for $250. ( Ouch! )
As far as I know, there are no chassis mods to be made. I'll keep you posted if there are