Hi Brian
This is what the sleeves should be and look like, I sent the timing numbers to you before, I can send the angle info to you also.
I think the pictures will explain it.
The sleeve on the right is a 51 size, It has 2 smaller boost ports with a hard angle upwards, these aim just in front of, and just to the sides of the glow plug center.the boost port in the 51 will be about 510 thou wide with a .110 (tenth of inch) bar in the middle.
The second photo shows the angle upwards of the ports
The third photo shows the ports from looking on the inside
The 4th pic is a closer look at the boost ports,
The main ports should be angled upwards at 30 degrees
As far as timing goes use 124 intake 135 exhaust, you can open all intake ports at the same time or drop the boost ports by 4 degrees, there will be no noticeable difference , this will make the 51 like an Aero Tiger, and it will do a nice 4/2 or a wet 2, or a strong 4 cycle, this will make for a very versatile setup.
Sleeve taper is important, I can talk with you about that.
Another thing that is very important is the sleeve top diameter, ST made several size sleeve thickness on top, and bore sizes in the heads, so some heads will not go down over the top of the sleeve, you will need to get measurements of these parts.
Randy