Proline mashers (or similar) 14.99/2
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXUM93

savage clutch and flywheel (you just need one pin and teh springs) 12.49 "buy it now" + 2.99 shipping. But you may find a better deal on ebay than that.

http://cgi.ebay.ca/NEW-HPI-Savage-21...QQcmdZViewItem

Then, If you want an alum clutch. You can get a nova set for 20.99 + 6.99 shipping

http://cgi.ebay.ca/HPI-Savage-X-Alum...QQcmdZViewItem

or

some mugen shoes for 17.92 + 1.75 shipping.

http://cgi.ebay.ca/Mugen-Aluminum-3-...QQcmdZViewItem

So if you were to go with the masher 2000s, and mugens, it would cost you 65.13.

Oh and you may want a second set of rims too so you can switch between these and the stock tires.
11.49 (per pair I think) http://www.customrccars.com/product_...at=22&custom=0

I am assuming you have the 11/14 (black and blue) pinions on there already. they are as low as you can go wtih CEN parts, unless you find something else that fits.

I just picked the first of each thing I found. you can probabaly do it cheaper if you scour ebay for a few days and compare prices.

Hope that helps