for a start you will need a 2tg to do the conversion
to stroke it to the 3t crank and rods and the 3t pistons
1st get some new oversize pistons from acl for 3t ,then you will have to fly cut the valve reliefs same as 2tg .
bore out to piston size and put crank rods and pistons into the 2tg block also while its apart ,get the head all cleaned up with new valve stems seals and get the valves reset into the head and also clean up the head face as well