The 86 block is not a roller block.
The roller blocks are different fromt the non rollers in that the bores for the lifters are taller in the roller blocks.
There is actually more material in the lifter bore, which makes it taller in the lifter valley.
Drilling for the spider is secondary...
I don't know if ALL the Lightning blocks were roller or not.
Around 94 or so, all 351w blocks were rollers. There was a change made to the actual casting of the block to accomodate the taller roller lifters.
The roller blocks will have an 'F4' marking
jason