Assuming a full engine rebuild:
- Crank measured and reground if necessary (usually is) by a decent machinist who knows about fillet radii.
- Likewise pistons/rings/bores. Fairly good chance you'll get away with a hone and new rings
- Balancing of reciprocating/rotating assembly including flywheel and clutch.
- Use decent bearing shells - Revington TR have got tri-metal big-end ones remade by AE for the TR6 - which uses the same shells. I think the OE Vandervell VP2 can still be found for the mains.
- Measure oil pump carefully and renew if needed. Note that new one won't necessarily be much better so measure this carefully too!
- The OE 1500 cam is very mild. A really good upgrade for road use is to get one with the Mk3 Spit (also Mk2 Vitesse / GT6 and 2500 PI) profile ground on a large journal cam (Canleys used to do these) which gives a nice lift to the mid-range while remaining perfectly tractable and without challenging the valve gear.
- New cam followers - suggest they come from the cam supplier but make sure they are FLAT not crowned (put two face to face with a fine film of grease and see if they stick together (good) or rock (bad)
- Clean all oilways thoroughly - you need to remove all gallery plugs and the distributor drive bush to do this properly.
- May benefit from some tidying of the ports immediately behind the valves. Dependent on how good or bad the original casting is a little material removal can make a big difference. Seehttp://sideways-technologies.co.uk/forums/index.php/topic/690-diy-heads/http://sideways-technologies.co.uk/forums/index.php/topic/6080-nicks-diy-head/
- Unleaded exhaust seats
- new valves and guides if needed
- re-cut seats with 3 angles
- Light skim to ensure it's flat
Use a Payen head gasket
Buy some new head nuts from Minispares
4-2-1 manifold is a big improvement over the cast 1300 manifold and still a bit better than the twin-downpipe 1500 one (doesn't blow the downpipe gasket all the time either).
The SUs will be fine but will probably appreciate a freshen up. New needle valves, jets etc. You'll probably need different needles anyway if you do any of the above mods.
Consider a mappable 3D ignition system (Megajolt is one example).
Consider an oil cooler if you do alot of open road, high speed driving, especially if you have no overdrive. The 1500 is the one Triumph engine that needs one IMO.
Should be possible to get a perfectly tractable, torquey and reliable 80 - 85 bhp