There is a thread on here that tells you how to go about building a repro PROPERLY as opposed to the usual dealer/trader or enthusiastic amateur method of just '.....screwing a set of dodgy pad on' and also screwing it up! Everyone to his own of course but to be absolutely honest and in my very limited experience in these matters as an Armourer, I know that there are all these barrel and this that and the other gauging limits and buyers do look for the brightest shiniest bore BUT. I have always said that what you want in a snipers rifle is not all the whistles and bells, but an ACCURATE rifle. And I have told snipers that we can re-barrel a sniper rifle barrel that has failed a gauge limit but when the sniper tells you that it shoots like a dream, then so long as it passes the Armourers accuracy test you have to take his word.
Tellingly, that is JUST the criteria that has been adopted for the new L115 rifle. The bore gauge must run freely and CHS up correctly. After that, regardless of the condition, if the sniper says that it is good, then it's good!
But that is only my limited experience in these things and 2c's worth
Anyway, what this is all trying to explain is that a reasonably cheap BSA made Mk1 that is accurate to the EMER spec. should make a good start to the project