1975 904 for slant 6

What is a good converter to get for stock 198 slant 6 ? Stall and diameter I see 10&11 inch . Not looking for any performance . Just good for cruising and lots of highway trips.

Not the same car this 1975 2 door dart if you must know . It's green , it has 4 15" wheels .

I work on lot of projects that aren't my own cars.
Are you sure about the engine being a 198 leaning tower of power??? The converter catalog I have lists only an 11" converter for the 225 engine, but no mention of a 198" engine. It is listed for 225 engines 1968 and up.