[ QUOTE ]
Where's Andrew Mace?? Andrew, please chime in!...
[/ QUOTE ]Mark, funny you should use the words "chime in"; in another part of my life, I play an 11-bell (Troy)
Meneely chime! But I digress....
I'd have to agree with Mark that there's no compelling reason to go with the 2.5L. He's absolutely right about the shorter-stroke 2L. And there's a ton of stuff you can do with it if you so desire.
If you do go with a 2.5L, you might as well grab at least a TR gearbox to go behind it. It CAN be made to fit and will last longer than will the stock GT6 gearbox. Then there's the diff; you'll probably have to do something there as well. Oh, and then better brakes WILL be a necessity, etc., etc.!
It's been a long time now, but in an earlier life I lived 24/7/365 with a 1970 GT6+ that I'd bought with only 20k and five years behind it. (After about two years, I did also pick up an old Volvo to relieve the GT6 of hapless winter driving 1. because it was already starting to rust badly and 2. because, frankly, the GT6 was NOT a great car to drive in snow. AGAIN I digress; sorry.)
Anyway, that GT6 went through just about anything and everything with me, including daily commuting, occasional vacation trips, and a whole bunch of road rallyes and autocrosses. Through all that, the greatest and only deviations from stock were 175/70R13s instead of the 155SR13s that would've been original (and the A78-13 bias plies that the PO had shamed the car with just before I bought it; fortunately a friend with a Pinto really wanted those tires, and I was happy to oblige) and a set of Koni shocks all around. The car was virtually always reliable, and it was a fine performer in every respect. It was comfortable enough that the ride impressed a Buick-owning non-car-guy neighbor of mine, but capable enough that I took my share of class wins in local autocrosses (even a couple fastest time of day trophies).
What I'm really getting at here is pretty much the same point I often end up making to new Herald owners, many of whom have the the notion that, just because their other car has 375 hp and every other gimmick and option short of a cappucino maker, their Herald MUST need instant and massive upgrades -- even though they've yet to even start it, let alone drive it any distance! My advice to those folks, and to you, is to start by getting what you have in the best possible condition. If what you end up with isn't to your satisfaction, then go S-L-O-W-L-Y with upgrades, and start with the "classics" such as wheels/tires; upgraded ignition, porting/polishing -- some of which are already on your list.
Oh, I did have a "sport" exhaust on mine at one point. It sounded ok, but the most noticeable change was the slow but sure creation of a flat-black rear valence (and license plate and lights....)
One other point of reference. Several years after parking that 6+ in hopes of an eventual restoration (I'm still hoping, 25 years later), I picked up a cheap and somewhat bedraggled, but mechanically sound '72 GT6 Mk3. For "lifestyle" reasons only, it didn't see the competitive motorsports events that the 6+ had seen, but it saw plenty of road use. Even though it had the "Federal" low-compression engine with only 79hp (compared to the 95 of the 6+), I never felt a great loss by comparison.
And earlier this summer, I went and test-drove another 70 GT6+ that a friend was anxious to buy. After brief drives by both of us, he very quickly negotiated a deal. What a rush it was to drive one again! It might only be 95 hp, but the torque is amazing...and so smooth.
So get it running well, enjoy it awhile, and THEN see if you really think you need to drop thousands into upgrades that might (or might not) yield some benefit. Triumph really did a pretty fine job of presenting a nicely balanced tourer in the GT6!