Hi Jeffrey,
Should be easy enough to do. The single block shown looks exactly like the lower block in my system. My upper block however is a double in-line block ie a larger sheave above and in line with a smaller sheave, this is a ronstan piece as delivered with my 2003 model boat. Don't know what the actual loads are but I wouldn't worry much either as you've still gotr a forestay attached if the halyard comes apart...no bit deal.

Also the keen guys in Oz are doing away with the pigtail at the top as this brings the lead of the rope further out the front of the mast. Attach direct to the mast tang and keep the rope close to mast for less interference.

Cheers Phil