I may just break down and buy the 450 retrofit kit. From what I can find on google 1994+ block were roller capable but most had non roller setups. Also keep an eye on ebay.
Any production F150-F250, E-series van 94+ with a 351 is a roller block (like posted above roller ready not equipped though). Rare would be the 93's that had the F4te casting (casting number for roller block) as some got them late in the year.