solid roller valve spring tool
http://www.yellowbullet.com/forum/sh...d.php?t=383384
These guys make incredible stuff but it is pricey:
http://www.lsmproducts.com/
This is their tool specifically for LS1 motors:

buxton engineering makes a nice tool as well:

If you decide to take the heads off I used a $129 tool from summit (TSF-TSW5000) that handled heavy solid roller springs with ease. Here it is right here:






