My employer refurbishes military vehicles for the Marines, cribbing blocks are all they use.
Yes I have made cribs to go under the front tires but you've gone way overboard. If a car weighs 1 1/2 tons that roughly 700 lbs a corner, a bit more on the front with the engine. If you use 2x6 on their side with stringers screwed to the ends you can stack them getting 5 1/2 inches of lift per crib. Rotate the cribs 90 degrees to put the stringers in an alternating position and screw two verticle pieces per crib to keep them aligned. The tops that go under the tires are made from drops with 2x2's screwed on top for tire stops.