As you see above ive got a 91 mazda 2600i its got like 130,000 miles on it... but still chuckin hard. i lowered the front with control Arms and Blocks in the back 4"... i get a real nasty vibration from my bed ive changed drive shafts and it still happens. my pinon angle is right on the money. i have ordered 3" lower leafs from a company off the web... to see if the blocks have something to do with it... anyone have any other solutions?
You seem to have addressed all the main problem areas. Wait till you get the leafs. After you install them if you still get vibration maybe the shaft needs to be balanced. Or you could check the transmission mounts. Maybe it your tires. If not just bite the bullet and take it to a shop, prefferably someone you know and have it looked at. I did the same drop on My 90 B2600i and I never had any problems, except that the aluminum drop blocks Broke once.