Manufacturers Web Sites:
We are in the process of adding some links for additional tool suggestions. Below is the Porta-Power. It's a pneumatic tool that we, and our full time contractors use in our shops. If you have more than a set of slings to do, you may consider buying one of these. They are about $140. Click the Image below to be taken to Harbor Freight where we get ours. Call if you have any questions.
These two below we don't generally recommend because of strength and torque issues. But we have heard from customers that the newer Dewalt XL series on the left works great for the spreading or bringing together of frames. We have since bought two for the shop and they will work on about 70% of the frames. This style has reversible ends so they can be used on both welded frames to bring in the sides as well as flipping the end and using to spread the frames. And at $35 they are hard to compete with. Try these first, and return if not strong enough. Click on the images below to visit their respective sites.
Couple of other ideas are to use "Car Jacks" like the ones that come stock in most cars, or small "2 to 4 Ton Bottle Jacks". Of course there is the ever primitive and possibly painful method of using two pieces of wood and a hinge to make your own spreading tool. Either way you go, you may need to use wood (cut 2x4 or 2x6) to get additional distance for your frame to meet up in order to avoid stripping the screws.
See Images Below for Examples:
And For At Home Repair in the Atlanta or Houston Area
Thanks and Have a Great Day :)