I got mine at harbor frieght for $45 bucks. They had 750#, 1000# and 1500# models, I took the middle at that price. I also invested in some decent 3 1/2 inch bolts and big washers to hold it onto the stand. Mine's a 351W and it's holding fine and easily wheeled around!
Best of luck,
I got the 1000 pound model at Harbor Freight. The casters were pretty poor quality, so I replaced them with stronger examples from Home Depot. Works okay now - the last engine it saw was a 401 AMC (the "Rambler" motor in my Jeep..) and now Lolita's 388 W. Works just fine so far, but it was somewhat marginal with the fully loaded 401. If I had it to do over, I get a stouter stand.