As the title says, what would be the effects if the ARVN won? Can South Vietnam last longer?
This was THE biggest intelligence failure of the entire war, which is quite an achievement under the circumstances. Theoretically they could have come up with a larger, better armed force for the offensive, but realistically if they knew what they were going up against they probably would have called off the whole operation, reminds me of Operation Market Garden in that respect.
The NVA moved in twice the forces predicted by MACV in half the time and had dramatically greater firepower then ever before. They were equipped with 130mm cannon which outranged the 105 howitzers and they had tanks to fight the ARVN who, like the US forces in the war, had never faced them and were not trained or equipped to deal with them. The planning was brief and based on the optimistic MACV assessment rather than others, such as a 1970 CIA assessment.
Actually siezeing the supply base would have involved a somewhat different operation, based on a more realistic assesment of the problem and needs of the force sent. It would have required the ARVN to defeat the NVA on ground it was totally familiar with and needed to have to continue the war. That achieved it would have cut the Ho Chi Minh Trail completely, so a long bloody battle of attrition would ensue. Without the trail supplies from the north would drop drastically in everything but I Corps ie the area just south of the DMZ. So yes, a victory would have fundamentally changed the war.
Damned unlikely though.