What is your castor set at?

What did you set the pre-load at on the trunion bearings (knuckle bearings) at?

How long are the front shackles from bolt hole to bolt hole?

How much drop on the front hanger?

What size tires, height and width?

Are your u-bolts tight?

Are the spring bolts tight?

Are the spring center pins tight?

There are a lot of things that can cause "death wobble".