I myself am not worried about high mileage as long as I know something of the history of the car. If it does not smoke and the compressions are reasonable, then IMO, if it aint broke, don't fix it. Unless of course you want a project for more power.
On another note, I cannot believe the extortionate prices for hotting up these engines. I was quoted a set of pistons for my 8v, at a tad over £400. Hells teeth! I bought second hand and in bits a Chevy 350 for my Cobra and changed everything. Pistons, cam, heads, carb, intake manifold, oil pump etc. The origianal BHP for the engine was 170. When I had finished, it was good for 330BHP. And the cost? For the engine and rebuild with mods, £1600. Set of 8 pistons including rebore and rings, £250. Although I bought some things second hand, it is still reasonable tuning with alot of reward.
God I miss that car!!!!!!!!