I'm mounting a 50 cal browning on my Italeri SAS jeep, in photos the ammo box is on the right side of the gun - I assume the feed could just be switched from left to right or is it more complicated than that?

Supplementary question

In many photos the round mags for the vickers K guns are seen just plced on the hood with no obvious means of attachment? How was it done? A magnetic strip?

I can answer your first question.

Its been 12 years since my days in the army reserve and my MG course but the .50 cal can be fed from either side. It required changing some parts around but as I recall it was a simple operation to do.

Jeff

Note that the 50cals mounted on the SAS jeeps were the light barreled Air Pattern M2s rather than the M2HB:
http://liberatorcrew.com/15_Gunnery/01_50cal.htm

The Academy U.S Machine Gun set has the M2 available in 1:35th:
http://perthmilitarymodelling.com/reviews/vehicles/academy/acd1384.htm

Sorry I should have made clear I'm makingn an SAS Jeep for NWE 44-45 where they did use the ground version of the 50 cal. Thanks for the website though.

I have a small stash of the academy MG sets, I used the air version barrel on my M4A3E8

An armorer can change the feed direction of the Ma Deuce. I have never personally witnessed this done since joining the Army, because there is no need to anymore. I have seen people who say "yeah I know what I am doing" disassemble the gun farther than operator level maintenance for cleaning, and put one or several of the parts in backwards, and then later at the range..."Hey this Gun is @#$%ed up!"

The only vehicle I know used a RH Feed were the M16 Halftracks (quad .50s) I can't comment on the SAS Jeeps.