Bill,
Since I have one, I will give you my impressions.
1. Consider making it only 24" tall. The sil height will be at waist high and you can bend over and into it easier. I'm 5'9", and the extra 6 inches hits me in the ribcage. Also, at 24" the sil is the next step up from a foldup kitchen step, making easy entry for projects like test mounting everything. It also puts all the suspension pieces at waist level which helps when you need that third hand. I use the engine hoist and the cloth tiedown straps for mounting the rear clip for test fits and it has to get pretty high for that, unless you always have someone to help out. There is a place right about in the middle of the wheel arches where it will pick up my clip level.
2. Consider puting either one set of wheels as swivel, or don't put wheels on one end and get a trailer dolly to lift the post not wheeled and it is easily moved. With wheels on front and rear, it will move every time you lean against it. I use a hand truck to lift the rear of my frame. The cross members are at a height that the truck just fits underneath, and when lowered, it picks the frame up. The truck acts as its guide.
3. I agree that you need hard rubber or poly wheels. If you like #2, put the wheels on the front as it has less weight to carry. The wheels may deform over time from a lot of weight.
4. Make the corner post from 6x6 post. Once you sink carrige bolts and
mortise the cross pieces to it, it won't "sway". I have a pic or two in a garge post here somewhere.
5. My stand is only 47" wide and the post sit just under the pan on the corners. 72" will put your frame into the rear wheel wells. Get the measurements of your pan and put the post on the corners. The corners ought to be so the rear wheels can go through their arc without hinderance. It won't make the rear too heavy. With the rear clip and spider on and the motor/trans in place and nothing on the front, it takes about a 100 lb effort to lift the front end of mine.(mine is a DRB/GT40 Australia that come with a steel pan attached).
6. Build the frame with the foresight of how you are going to get the car off it when at that point. Mine has the front crossmembers and posts as a unit. I secure the side frame rails to the frame of the car with nylon ties(it will become apparent in a minute).Lift the front of the car with the engine hoist, remove the front posts/crossmember piece. Lower the car(the ties will keep the frame rails from flipping away from the car), and move the hoist to the rear and raise the rear of the car. Remove all frame pieces, and lower the car. Reverse for mounting on the frame.
Here is the thread on dollyswith a pic of mine.
Bill
Here