Once again thanks very much for all the detailed and informative responses...
Charlie - Yes, I'm definitely going to take it to a rolling road, there is apparently a really good one in my town which is classic friendly.
Alec - Thanks for those pointers, I'll have a chat to my neighbour and see what we can sort out.
IslipMinor - Wow, if I could get 100 bhp and 100 lb/ft torque I would be a very happy bunny! Presumably the 20bhp over PSL's quoted figure comes from the balancing and the overbore? These are mods out of budget for the moment unfortunately. What is a main bearing strap used for?
I forgot to mention originally that I will be using a K&N filter and stub stack also.
The quoted CR for an Ital engine is 9.4, should I be looking to increase this at all?
Roy - Thanks for looking for the valves, no worries, I'll just buy a set new - still cheaper than a big valve head

I'm probably not looking to be revving past 6000, I just want to be able to use it for 'spirited road use', so it looks like the Metro cam or a 266 is on the cards. Do you know the 'number' of the metro cam or a Kent version that is similar?
hotrodder - I saw your manifold in another post and its most impressive! Can't believe you got all those bits looking so shiny - was that all hand polished?!
LA - thanks for those comments, an RC40 single box is definitely another option and they do sound really good... going to keep my eyes peeled on ebay to see if one comes up cheap. Though part of me really wants a cherry bomb, just for the 'heritage' factor, and I just love the raspy note
I think to begin with I'll crack on with a standard head, metro cam, modded HIF44 and inlet, K&N and exhaust as mentioned and then approach the head porting and larger valves on the spare head and fit it as and when I get it done.
Thanks again, G