The exhaust manifold on the 310 engine has the pipe in the same position as your 1800 A diesel so that hole in the hood will match. I have never done this but you should not have any large problems. There will be small items that will require some thinking.  The first is the air cleaner as your a series probably will not have the flow necessary to supply the engine if you work it to the full 90+ horse power. Also it is rated at 2400 RPM while your diesel is at 2000. External appearance will be most noticeable on the right side mainly with the oil filter locations and on the left side with the carburetor. We did convert some A model gas engines  to 283 B engines with the larger intake and carburetors. They worked well. More questions?