Hi Ed, is a T-18H a 2 ton truck? or bigger. I have not got my engine out of the truck yet, I am going to remove the cab and then remove it, but I did remove the manifold and can measure the spacing if you like. the brochure I got said that a F-33 and a F-33HD had a 286ci in these cabovers , as soon as I get the engine apart I can check out what bore and stroke it is, its is possible that they(GMC) made three piece engine with different bore and strokes , maybe if you measure the front port to the rear port on the head, we can compare them to each other. Dan

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1936 1.5 wrecker,1937 gmc coe,1939 Chevrolet coe,1942 4x4 coe, 1942 coe,1946 dump,1947 2 ton dump,another 1947 2 ton dump,1950 coe,1967 c30,1937 cat 22,1936 Chevrolet 5 window foremans coupe, 1914 ford speedster.