I believe it is already a roller cam motor, but they do not have Provisions for a spider.

That dont make sense.

If its got roller lifters it got provisions for the spider and dog bones.

It could still be a roller block but of been built with a flat tappet cam.

You best bet is to look in the dizzy hole or pull the intake OR you cam pull the valve covers and look for the large diameter pushrod holes in the heads that are that way to make up for the tall roller lifter pushrod angle.

During that transition time ive some heads with the same casing numbers, some have the pushrod holes drilled larer, some dont.

Its all sorta a confusing time period but easy to bone up on and make it all simple,

The search engines that lead to fabo and all par are semi good resources as well as many here that know alot more then me.

But if you do it the last way id use a big light to look down the pushrod holes for the dogbones or turn it over and look for the big sweep of the pushrod as it cycles.