I heard it was mid '93 when they started. But this I'm 99% sure of, If ithe block casting number(behind the starter)starts with F4('94) it is a roller block. The F2('92)and earlier blocks are not cast for roller lifters, and I have not heard of a F3 block.
I believe you'll be looking for the F4xx lightning block. This part number 'F4' stands for 94. I don't know if it was released in 93 or not. But I'm pretty sure F4xx is the right casting number to look for.