in my opinion; the more aggressive the lobe is the more likely a camshaft can't be successfully swapped from block to block. the xe268 is an aggressive lobe and the tappets that were used in the initial break-in weren't used, plus the tappet bores not in exactly the same location with the two different blocks can be a problem. i'd just move on to a gentler flat tappet cam. $1500 cost for the roller set-up was mentioned. i'll bet the cost to convert will be well beyond that. most likely the heads will have to come off to set them up for the roller, $$$. if one is willing to do their own work a proper (that's for the OP's intended use) hydraulic flat tappet can be done for around $300 and would be more reliable with less maintenance in the long term.