"special high performance" 360?

Numbers on the side of the block are in general numbers. You'll need where there stamped below the cylinder head drivers side for any special info on the engine.

Special HP engines came with double roller timing chains, windage trays, HD springs and a 340 cam. like an E-58. (Cop Engine)

Yep, you will need this number.
If it is a special performance, there will be a 3 right after 360.
Sequence like so: ? ? 360 3 then production #'s
The ? ? are Date & plant #'s
Hope this makes sence.