Geezer,
I put that combo on my 248 GMC. It ran great, (for about two days), until the head gasket blew, (no fault of the carb, just age) - From the limited experience I had with it it seemed to give the engine a little more power but I never really got to put my foot into it. Hopefully I will have the truck back together this week, I could give you another report a little later on.
Also, when I bought mine they had rebuilt but also had some new carbs for $10 more. I spent the extra $10 and got a new one. You'll also need the linkage kit and air filter from Langdons, (that carb has a unique throat that requires their air filer), so your looking at another $60 or so, (don't remember the exact amount), over the cost of the carb and adapter.
