All 3 of the crawlers you listed are shaftys. If you're looking at going for a scaler...why not buy a scaler to begin with? It's pretty likely that if you converted those rigs to a scaler that you would invest as much, if not more money than you would have if you bought a scaler in the first place. Here are some things to think about:

Do you plan to compete? If Yes, buy something comp worthy...an AX10 is a good start for a sportsman rig, but a MOA rig would be more competitive.

What's your budget for EVERYTHING (crawler, electronics, battery(s), charger?

Do you want your rig to be able to climb over most things in sight and articulate like a circus contortionist...or are you content with sacrificing performance for scale looks?

What do other people in your area run? If everyone runs scalers and you buy an AX10...I can almost guarantee you'll convert it to a scaler.

If you know other crawlers in your area...befriend them and ask them if you can run their trucks, if you've never ran one before. Then you'll get an idea of what you like and don't like.<br type="_moz" />