Cement blocks are fine as long as theyt aren't cracked, they are placed with the walls running vertically, and you put a board across them to spread the load over the whole surface. Point loading them, such as letting the frame rest on just the edge, will crack them. For stands, you could build simple 2ft square, 2x4 box cribbing. 2 will support a truck no problem, we used to use them to support 15 ton granite slabs. Like this.

 

The solid concrete blocks look like this:



Use a cribbing pattern (2 X 2 crossed) will create a very stable foundation for standard 3 Ton jack stands. I have used these solid blocks to support 40' shipping containers that weigh a whole lot more than a truck. For the shipping containers, I add a 8X8 timber across two of these pilings to spread the load and absorb some movement. That might be overdoing it on a truck.