I made mine out of spare 2X6's. If they weren't free I would of used 2X8's (tread weidth on tires for E-450 around 6.5 inches).
3 boards for each "ramp", bottom is 3 ft long, middle 25 inches, top 13 inches. All cut with 45 degree edge. Used lag bolts with rounded/dish shaped head and counter sunk the nuts on the bottom to be flush.
I have two sets of those Lego blocks also. If I'm wearing old pants, weather is pleasant, and I'm trying to take as long as possible to setup... I'll dump them all out, get down on the ground, stack them up like a pyramid, and hope I guessed right how high to build it so the tire can rest on the last and only somewhat flat spot of the pyramid.
Go can probably tell which leveling "technology" I grab 95% of the time and which one I use as a last resort. With the wood ramp "technology", I just drop them in front of the tires, slide them into position with my foot, get in and drive forward one level at a time. If drivers front is lower, I drive up only on that side until level left-right, then slide the second ramp under passenger tire and continue driving up till level front-back.
2011 Sunseeker 3170DS - 30,000 miles explored