Dip stick tube?

[Hawssie]

I know this going to sound stupid and easy to figure out but I am having trouble figuring out what dip stick tube to get for my engine. The truck Im working with had a 1969 307 in it. But it had a funny engine code that no one could figure out because it has a CE number that says it was from the early 60s originally a 383 and was an over the counter replacement engine I think. Anyways I am now putting in a crate motor 350. Its been sitting around on a stand for 6-7 years and I think was one of those 300-330 hp engines GM was selling back then that is the newer one piece oil seal block with the Vortec heads. Anyways they were really popular back then and maybe still are. I never dressed it out fully and now am. So I go to put the oil dip stick from the older engine into the new one and its diameter is to big. The older engine has a 7/16 hole and this one is a 3/8 hole. I looked up and down online on Summit but nothing is ever mentioned about diameters, just years and it seems to be all over the place. Is the new engine the typical size or is the old engine the typical size? It seems easy enough to order one for a "Small block" but I want to make sure Its going to fit.