We used to shoot 45/70 and 45/90 through Pedersoli's. My mate Shaun has the Quigley version which is simply beautiful, his Dad has one with a period 6x 'tube sight' CLICK.
The scope's are seriously expensive ( for what is essentially a x6 power, fixed brass tube optic ) and is adjusted via the mounts. We never found any benefit in accuracy using the scope over the excellent diopter sight, infact accuracy suffered a little as the adjustable mounts would wander under recoil - but the rifle looks the absolute nuts with a three foot long brass optic on it ( and Josey Wales used one so we left it on ).
The 90's aren't as accurate as the 70's but are so much fun to shoot, especially with BP as there's tons of kick and smoke
From memory there was a price hike and even the base model Sharps rose to over a grand, the Quigley model costing over two grand. I would imagine Henry Krank is still the place to order from and around £1500 would secure a decent model.
Middaycowboy/Tezz, if you'd like more info on them, pop along to Wedgenock Rifle and Pistol club in Warwick on their open day ( you're not a million miles away ). There are tons of people using them there as that particular club has a range velocity limit ( meaning you can't use a 250 fpe hmr rifle but a 5000 fpe Sharps is no problem ). They're great rifles to own.

ATB, Craig