I can't speak to the performance of a H/W on a 250 as I made the conversion on my 1956 235. I found it impossible to find a decent Rochester/Carter core that didn't have an excessively worn throttle shaft and the same warped air horn so commonly found on the Rochester. I got with Tom L., took his advice and the H/W met or exceeded my expectations right out of the box. When I built up a 1960 235 with all of the normal upgrades, I found that a set of dual Carter/Webers gave me the lower end performance I was after. I was after a "cruiser" engine that made it's torque between 1600-2400 rpms and my 54 truck with a .72 T5 and 3.42 R&P will cruise all day at 70 mph @ 2000 rpms and I AVERAGE 18-20 mpg.
Tom is pretty adament about his "water heat" but I went with the exhaust heat, using an infrared thermometer, I verified that it DOES provide quick heat and after 4500 miles I've noted NO ill effects. The level of performance was excellent with both the H/W and the C/W's. Granted, they do not "look" like the stock carbs but 9 out of 10 folks who comment, mention how the stock carbs just didn't provide great performance even when new.
As you've probably guessed, I'm completely sold on the H/W's and C/W's. If you have access to some good stock carb cores you might be able to retain the "look." However, if you're looking for flawless performance, ease of installation and tuning, and a reasonable initial price, than you might consider the Langdon setups.
Dave
