It depends on the level of ToT given- the FH-77Bs came with full ToT that allowed India to produce them from the ground up in India, that these plans sat idle literally in some MoD file cabinet for decades untouched is another matter.
AFAIK the M777 arty tractors are going to be TATA trucks (LPTA 1623 6X6 most likely). But you make a very valid point about the air-mobility of this gun, that is the primary consideration behind its purchase, alongside the IAF's CH-47Fs:
Indeed, the M777 is for the MSC and the key element is being air mobile (ie can be underslung from a CH-47F). The MGS (and SPG) are for rapid movement of firepower to keep up with the Intergrated Battle Groups (IBGs) that will contain MGS, MBTs, IFVs, BTT, SAMs, and all associated support vehicles. The idea is for self contained elements able to make rapid thrusts into enemy territory independantly.
Ceasar and Archer are 155mm/52 while M777 is 155mm/39. Same calibre, different barrel length.
There would be little benefit to a truck mounted M777 as its primary benefit is being light weight and thus air-mobile. The M777 is made from a high degree of lightweight materials such as titanium but this also makes it comparable expensive. For MGS/SPG, longer barrels are used for greater range.
M777s are meant primarily for the MSCs (ie the Eastern theatre).
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