Benefits include reduced value gear wear and less power loss. The increased ratio will provide higher valve lift.
It may be necessary to use an aluminium rocker cover of the RTR1075 series as the rockers may foul the standard tin cover. Please check for clearance before starting the engine.

GENERAL INFORMATION
There are two types of roller rocker sets, varying only in the ratio between camshaft lift and the resultant valve lift. The standard ratio for a Triumph TR2-4A and TR250, 5, 6 is 1.55:1 meaning that for every 1mm of camshaft lift, the valve will move 1.55mm.
1.55 :1 ratio is the standard ratio and will change nothing with respect to the engine set up but offers less resistance in the valve train bringing longer life to the affected components and to a very small extent increased power due to less resistance for the engine to overcome.
1.65:1 ratio increases the lift from the same cam, offers the same benefits and the 1.55:1 set and can increase the performance but this by no means certain as the condition of the engine and the components in it will affect this. Also, the extra lift has to be accommodated by the components in the valve train. A competent mechanic needs to check that the valve springs will not become coil bound, the rocker geometry is adjusted, the push are the right length and that there are no interferences between components.
After all this has proved satisfactory the engine will need re-tuning on a rolling road for best results.
Revington TR can undertake this work on their 400hp rolling road.