Hello. I took my 75 out for the first time this year after it was parked for 3 months to wait out the winter. Drove the car about 1 mile before I got on a road that I began to open the car up on. As soon as the speedometer hit 43 mph, the car began to shake violently. As soon as I slowed down it would go away. The steering wheel doesn't shake at all just the whole body. I got the car back home where I jacked it up. Looked at the front suspension, cheacked all the lugs on every wheel, checked the driveshaft and everything looks perfect. All the weights are also on the tires. The only thing I can think of is that the weights might have shifted and the tires aren't balanced anymore. Any other ideas?

Maybe the tires have flat spots due to sitting around all winter. If you drive on them long enough I think the shaking will stop.

I would check universal joints on half shafts and drive shaft.I had same shake and found 2 bad universals,they were change problem gone :D