That's great Glenn! I paid 69 bucks for the one I have. I was going to build one a few years back and put the dial indicator I used for setting up differentials when I turned wrenches but I found that for some reason I had cut the mounting boss off the back. I think is was just in the way for the way I was using it. At 69 bucks the one I got came with a new dial indicator so got me up and going a little faster.
Sure. Here you go. The dial is fastened off center to keep the knob from getting in the way of the touch-rod. This is not always an issue so feel free to do it anyway you like. It is important that the piece that the dial fastenes to makes contact with the table top. That is, the piece that sets in the miter slot should not be able to touch bottom.
I don't know for sure how accurate the HF unit is. I hate to say this, but, I never thought to check it. I am sure my physics and chem professors are all rolling over in their graves because of this lack of checking. However, I have been using one (HF) for years to line up the TS, etc. It seems to work fine.
I used some scrap maple, three flat head machine screws for a solid contact in the t-slot and inset a cap screw and knob to clamp the dial indicator in a fitted slot. The jig I made isn't as versatile as Glenn's, but it's solid.