lowering block material?

[13lazer]

i had no intention of lowering my '70 c5 blazer, then i installed stock height disk brake spindles. i got a "free" 2" drop i hadn't planned on and the 33" tires i was trying to use up started rubbing the fenders. i have a set of 17" aluminum wheels with 265 70 r17 tires from a sequoia, or a gx 470 depending on what center caps i get. i am waiting on some spacers to finish installing the lexus wheels on my narrow rear axle. i used the body line to measure the distance to the center of my hubs. the rear of my truck is about 5-1/2" to 6" higher than the front. 4" with the 17's installed. i want to stick 2" blocks between the axle and the trailing arms to level it out. my question is, would a very solid piece of oak hold up as a lowering block? i know one of oaks properties is weather resistance, and i think it wont compress. i cant drill through anything else i have thats 2" thick. this is a really nice piece of oak leftover from my basement door project last year. is this a bad idea? is anyone around here familiar with both truck suspension and hardwoods? i'd like to hear some opinions. should i keep the grains vertical in compression, or should i cut the blocks so that the grains are horizontal in compression. i want to avoid having the oak block split while im on the road? or should i just hunt down some aluminum?