i'm installing a edelbrock performer intake and a edelbrock 600 cfm carb on my crate motor and i'm wondering what to use for a throttle return spring and where to get it.

You can pick one up from any auto parts store. Advance, auto zone......
Double springs, run it to a bolt on the intake or the throttle cable bracket.

You can do it 2 ways..

Any auto parts store will sell single and dual carb return springs

See the very top BIG hole in throttle linkage on driver's side of carb.. You can hook spring there and pull it foward (towards front of engine)

Or theres a little tiny hole in the very bottom of linkage.. You can put spring there and pull it back (towards rear of engine)

If you go foward with it, then you can buy a $2 little chrome L bracket that will bolt to intake using one of the intake bolts, then spring hooks to it.

If you go rearward with it, you'll need something like a throttle cable bracket that hooks under the rear carb bolt, that has a hole in it from spring, then hook spring there.

I just completed the same carb swap and I opted for the forward spring. It wokred out just great although the first spring I got was very stiff so I opted for a double spring set up. I can send a pic over the weekend to show you.

please send a pic. thanks

Here are some pics. One is of the mounting bracket. The other two show the springs and how they attach to the carb if you are mounting forward.
4081

4082

4083

Here you go... You can see the return spring bracket on the second intake bolt on driver's side in these pics. (these pics is from when I was 1st putting engine in my car, so no carb on yet)

http://rides.webshots.com/photo/1125466329041290424wCgHfw
http://rides.webshots.com/photo/1125466948041290424IxwNVh
http://rides.webshots.com/photo/1125469330041290424tzLAnB


In this pic, the engine is all together, running.. You can see the red dual spring going from carb to bracket on intake, but from the angle of pic the rad. hose hides the bracket.
http://rides.webshots.com/photo/1289807040041290424nZhXFa

This pic shows it pretty good.. Engine bay is dirty though, just got done drilling a fiberglass hood for hood pins so all the white drilling dust is everywhere.
http://rides.webshots.com/photo/1535346731041290424EJYNVO