Those look just like the ones that come with the "pro" model of the Sunfish, but yours have rollers, I think they are legal, I'm sure someone else here can let you know for sure. But if you are just speeding around, they will work for sure.
Yup, the 236 Harken clam cleats are legal. You might want to get a pair of thimbles to complete the rigging.
I don't have a diagram but here's my best shot at discribing how to rig them.
Outhaul: The cleat mounts on the lower spar with the roller facing rear. The line runs from the sail through the hole on the spar end and then you need to tie off a loop (that's where you put the thimble) that will be the third purchase. Then the line goes under the roller and back through the loop you tied and then back under the roller to the actual cleating surface.
Cunningham: The cleat mounts with the roller facing foward on the lower spar. The the line is tied off on the first sail grommet above the lower spar. It's then run through the hole that's formed by the bottom of the spar end so the screw won't hit the deck. Then again tie off a loop (with thimble) and run the line under the roller and back through the loop and back under the roller and intot eh actual cleat jaws.
This will give you a triple purchase for both outhaul and cunnungham and the thimbles keep the lines pulling easier and won't hang up when releasing.
I mounted the cleats on the side of the spar opposite the mast so there would be no interference with the mast.
I added loops at the free ends of both so grabbing them was easier and I used 1/8" Spectra line. Larger lines might cause some binding under the roller on the cleat from the multiple lines in that area.
One Note: ALWAYS release them after sailing before putting the sail rig away. I learned the hard way one fall as my last sail was 20+ knots of wind and I had them both pulled hard to flatten the rig and the rig got put away. Come spring I was being sailed bye, by boats/sailers that normally only saw my stearn. Come to find out the sail had stretched to the point that it was unusable for racing. A costly lesson.
The thinbles are for the loop, not the roller. Besides the rules DO allow them:
"3.5.6 A total of two lines and two cleats may be installed on the spars to facilitate adjustment of tension on foot and luff of the sail. Only one adjustable outhaul/inhaul is allowed for each spar. Lines may not be led internally in the spars. Any number of purchases may be used. These adjustable outhauls may be led through flexible fairleads, attached to the spars without hardware. It is permissible to use a thimble, or similar device without moving parts, tied into the purchase loops to prevent chafing of adjustable outhauls. This device shall not be attached to the boom."
While I prefer pop rivets, epecially ones with what are called rivet cups that effectively seal the rivets (the center will leak, it isn't air tight with out the cup) I used simple stainless flat head screws that fit the recess in the ends of the cleats and caulked both under the cleat and the screws during installation to make sure no galvonic reaction would occur if I hit salt water.