by Steve J » Thu Sep 29, 2016 9:34 pm
The later Indian GP headsets use a gearchange casting and light switch housing which are considerable 'fatter' than the Italian versions, and the main castings are thicker to match - about the same diameter in that area as the Series 1 & 2 castings. Supposedly done to prevent the headset casting breaking on Indian roads.....
The early Indian GP headset castings are identical in shape to the Italian ones, and even have the same part number (although the part number stamping is completely different.) My GP curryburner is a 1976, and came with the thinner headset -which needed some welding. Good luck with getting an early Indian casting - they do come along from time to time, but some of the castings aren't too good, and need a bit of welding/filling/fettling. The alternative would be to fit the later type GP headset, but you would need to get the matching headset top, the gearchange casting and light switch casting. These later headsets often have the bosses cast in for fitting mirrors.