Two of just about any kind of carburetor on an inline six is either one too many, or one not enough. The intake port setup on the stovebolt engine is just begging for three VERY SMALL carburetors. Two YH's on a 235 is WAY too much carburetion, which almost inevitably results in lean surges, backfires, and generally terrible performance anywhere except wide open throttle and high RPM. If you insist on using two carbs, try a couple of Carter W-O carbs that fit the CJ-2 Jeep flathead 4 cylinder engines from WW II and the early 1950's. Those will only be slightly over-carbureted for a 235 engine. I've got a bored ands stroked "261" engine on the drawing board that will approach 300 cubic inches and run three side draft Keihin carbs from a Harley Davidson engine.
For instance: This one's got a broken throttle base casting, but it's only pictured for reference purposes.
www.ebay.com/itm/334754230247?There are a lot of brand new offshore made "clones" of the W-O carb- - - -"buyer beware!" The quality control probably isn't great on those things!
Jerry
