As rules I recommend Charlie Do not Surf from TFL. It plays well in 10mm, (company sized games, I think that 10mm it is perfect, if I did not overspend in 15mm... but pendraken is tempting).
You play the period and there are plenty of interesting scenarios.
As basing, I would say 3-5 men (only the USMC had fire teams at the time). Thus a PAVN/NLF squad will be two stands (one 4 one 5) and you can mark casualties). Three 4 men bases give you a full (rare) USMC squad, while the army was usually around 8.
Arrigo