Not one for those new fangled inlines (nothng wrong with them, just not my cup o tea), I agree with Cayugad on the Green Mountain IBS system for T/C Hawkens and Renegades. A lot of choices in caliber plus you can get most of them in blued or stainless.
But Lemoyne was also right. You get a .32 cal 15/16" barrel and that sucker is a good bit heavier than the same barrel in .54 cal. So I guess its a trade off of weight for convenience of swapping calibers.
Speaking of which, there is a nice T/C Hawken flintlock in the classifieds.....