Guide
here
I haven't looked in a while, but GTA Tippmann Ebolt kits, if you can still find a decent one, probably go for way more than they're worth. If you have access to machine tools, I'd say make your own. It will be better and possibly cheaper. If you start from scratch you can go all-out and two-way the ram.
I'd recommend using:
-Scenario Dreams Universal T-board; about $55
-5-way solenoid of your choice (if you two-way the ram; if you stick with a spring-returned ram then you want a 3-way solenoid); a wide selection of solenoids can be found at airsoldier.com, price will vary
-LPR of your choice (cocker LPR's work great; can be found as cheap as $10-20; I'd recommend a Palmer Micro-Rock or AKA SCMIII, but those will run you upwards of $50)
-Ram; if you cut it yourself you're just looking at cost of materials; otherwise you can find machinists that will make them for around $100