The Vortec head uses center bolt valve covers, so your old ones won't fit. The 12558060 heads are advertised to be good for 0.475" lift, but be sure to check the clearance between the seal and retainer if your cam comes anywhere near that much lift. In some cases, insufficient clearance is caused by the valve stem seals not being fully driven down on the valve guide boss, so if you're having clearance issues w/a cam having less lift, check the seals for being installed all the way, first. If your cam is stock this won't be a problem.
If you want to get the mostest from this swap, read up on the quench
measurement. You will have the opportunity to improve the quench distance (if needed) by using a head gasket w/the thickness that best suits your engine. It does require some measuring, but nothing that you can't do I'm sure.
Other reading, if you're in the mood:
• Vortec heads
• Valve spring installed height
• Valve train points to check
• Valve train geometry
• Adjusting hydraulic lifters
• Cam break in
(not needed unless you were to change cams)
• First start up
. Mainly useful for getting the distributor back in so it'll start back up easily.
• HEI distributor/Timing info
- this is very important, especially if the distributor you have is a stock unit. You can gain good power/improved drivability by dialing in a performance advance curve. The stock curve is the pits
in almost every case.