The same K-member was used for slant and V-8 in 1965, so that can't be the problem. The 318 block is identical externally to the 273, so not the problem. Only the 360 block differs in different motor mount ears and a larger rear bearing diameter (special oil pan needed).
I had later thin mounts on my 273 initially to try for more hood clearance (plus cheaper), then swapped to the original thick ones so my later Federal pump cleared the K-member. The oil pan was above the K-frame with both. Of course ~1" higher now with the thick mounts, and I need that since I found the steering linkage just barely clears the starter (apparently hit originally, see my post). I didn't have the steering on then w/ the thin mounts. Anyway, I think you require the original thick mounts to clear your steering. Pretty sure my steering linkage is for V-8 since that is the fender tag. My 64 slant's linkage is currently off and looks almost identical. I'll try to measure and see if the V-8 one actually drops more (maybe 1/2"?).
I am at a loss as to why your oil pan sits on the K-frame. That sure won't work. Best theory is that your engine is too far forward (66Dvert). Post photos. The distributor should be real close to the firewall. That is why they put a recess for it. People w/ 64's must bash in their firewall to install a V-8. Otherwise, you should have hood clearance with say an Edelbrock Performer 318, but may need a drop base air cleaner and 2" element, depending on carb. Is your Street Master a tall long plenum type? You might need to cut a hood scoop for that.
