Depending on the rim, beadlocks will be somewhat heavier. On my Top Dragster, I went from Weld Pro Stars to Mickey Thompson beadlocks. I went with the mickeys because they were about 2-3 lbs lighter than the Welds and are one piece forgings...This was before weld introduced the new Delta wheel. Anyway, my old wheels weighed in at about 15 lbs each, where my beadlocks weigh right at 23. However, they made a huge difference in how my car reacts off the line and down track feel. I'll never run a car again without them unless it's a 10 second or slower car. But then again, I have zero intentions of ever slowing down. They aren't cheap, but I believe they are a worthwhile investment, and they are safer than regular wheels. Nice thing too is you can mount your tires yourself without anything other than a ratchet, socket for the bolts, and a torque wrench. Get a quality bubble balancer and some stick on weights and you're golden!
As to if they will affect et, I've seen it go both ways. Some cars will slow slightly due to the extra weight, I've seen a few pick up because they solved tire issues they were having. But for your deal, I'd make the investment. If you plan to go faster in the future, you'll need them eventually. I have a buddy here with a 9 second dragster that just installed them with bigger tires on his car. Went from a 33" tire to a 35". Car only slowed a couple of hundredths in his 60' and et, and lost only about 1-2 mph on the top end. But his car is way more stable and is way more predictable off the line. He's going to step up the hp a bit to recover the lost et and mph. But in his words, they were some of the best money he's spent.
Owner/Driver of the Livin' The Dream rear engine dragster
Speed kills but it's better than going slow!http://www.livinthedreamracing.com
Authorized Amsoil Retailer