69 camaro convertible, 3950 lbs with me in it. Car has a corvette c5 front end, rear suspension has Hotchkiss springs, cal tracs bars with no preload, pinion angle 4 degrees down, mickey Thompson drag radial pro's, 275 60 15 on 8" rims. Car used to hook up fairly decent and something changed. Used to run a 1.45 60, now I'm at 1.6 or so. Tires don't look bad to me, but I did order new pro bracket radials, haven't run them yet. Car has stock style shocks front and rear. Just bought a set of viking double adjustable shocks for the front, unsure if I need to do the rear. I also just bought a transbrake valve body for it, any suggestions on what to do? Car used to run 9.75 at 138, and yet I'm still within 1-2 mph of that but not getting the et.

 

https://m.youtube.com/watch?v=PsYK_3JvhPs

 

Get your corner weights. Made a world of difference for me once I dialed in the rear weights. All setups will be different I'm sure, but dialing in equal rear corner weights and making sure you have at least 40% of the total weight on the rear should be the first step IMO.

The more power I added the more I had to stiffen the extension of my rear shock. Compression is also very stiff. I can jump up and down on my rear bumper and it doesn't move. Not saying that will work well for you, but if you added power it's likely you need to stiffen things up in the rear.