Hi Bob
Well as you know from Rob the original 216 CMP drain pan has the plug on the bottom center rear. Now for the fun 235-261 truck drain pans plugs on the US engines I have have the drain also at the rear center of the pan. My 261 though has a special heavy truck 4x4 pan that I found NOS which has the plug located at front center on the bottom of the sump. The sump is different shaped from the standard US truck. So I guess the answer is there are a number of variations.
Your over rich problem with the carb may be a float adjustment problem or a fuel pressure problem. (over pressure) Look at the fuel preasure spec first page of
http://www.canadianmilitarypattern.c...e%20Manual.htm
I just got a full rebuild kit for my 261 carb and discovered that the float was set to wrong. Engine has even more power now than when you last saw it.
Did loose one important feature in going to the 261 I lost my cruise control. With the 216 you could get on the highway and just put your foot on the floor and forget it. Now with the power of the 261 you actually have to control the speed of the truck.
Cheers Phil