Since you've jumped into the Vietnam era, the M48A3 with 90mm gun would be a good companion piece to the proposed M113 kit as well as the proposed (plastic or resin) M551 Sheridan.
One of the great aspects of your kits are the options you include. In this case the options could include the following: USMC flame-tank version of the M48A3, the 105mm-gunned M48 that was present in US forces in Europe, and the 105mm-gunned M48 as used by the Israelis (different commander's cupola).
Not only would an M48 kit enable US Armored Cavalry actions in Vietnam (the Sheridan didn't deploy to Vietnam until 1969), but it would open up the Arab-Israeli wars since you already have (or will soon have) the M113 and the M3 half-track in your line (you could do a bonus sprue with M3 weapons / cargo specific to Israeli use). Of course adding the Israelis would lead to adding post-war Soviet kits for the Arab forces - but that's another wish-list altogether.
