What Rardi said
Rardi makes some good points about the sheeting angles. For most of us with furlers (making for lousy sail trim) and other goodies, we're not going to notice or benefit from very precise sail trimming. Pull the thing in against the spreader boots and see what you get.
The barberhaul is a good idea too; but, again, it's not the clew location that's limiting you, it's the center of the sail pulled against the shrouds. So aside from putting a crease in the sail shape, I don't know what a barberhaul is going to do for you with a 135 or 150. (Remember that barberhauls came into prominence during the early IOR, 1968-1974, when boats were deplorably wide at the shrouds and narrower sheeting angles were just a matter of sanity. We with Hunters don't have that problem.)
The one benefit to taking the genoa blocks off the rail is the preserving of the rail. Stainless-steel snatch-block shackles wreak hell on the old aluminum-- and this is a part that is, more or less, utterly irreplaceable. The constant sawing of those shackles over the years has probably cut grooves into the aluminum itself, let alone destroyed the anodizing. Wichard and some others make rubber-padded mounting eyes to install in the toerail; but they are very expensive (perhaps I should say VERY EXPENSIVE) and you'd need maybe three each side (since they don't remove very quickly, not like snatch blocks) to provide some variation in sheeting angle or for different sails. That's an investment of about $1200.
As an alternative you could use Dyneema loops; but despite all Dyneema's strength it's still able to be cut with a knife, and rather quickly (hence the ORC requiring it for lifelines at sea) and that sharp edge of the toerail openings would make short work of it.
The one real fear I have about installing genoa track on Hunter decks is what you will do about the core material. The moment you start drilling holes in the single most vulnerable spot of any older Hunter, the moment you condemn the boat to major health concerns for ever. You'll have to provide adequate backing plates, like out of G-10; you'll have to bush all the holes with compression tubes, like out of G-10, and you'll definitely have to bed it with 5200-- and for this there is NO substitute. These are three bits of advice from my expertise which too many people with much less experience than I have seem to gainsay on here; why I don't know.
And, of course, you could always guess wrong and install the tracks on the wrong angle or at the wrong distance aft from the mast; and then what do you have?
Best, of course, is to experiment amply. You may find many other solutions that could do other things for you. The last bit of advice I read on here may be best of all-- get new sails. The boat didn't sail all that badly when it was new-- merely bringing it closer to an as-new condition may be the very safest, cheapest, and most technologically advantageous of all your options.
