Chevy v8 kits, manuals, etc. can be obtained through these vendors:

www.jagsthatrun.com - premier site for 240z v8 kit and *manual* - known worldwide as the best v8 z manual out there. Now offering v8 kit for the 280zx. Also carries aluminum radiators, headers, etc. These items are all custom to fit the z car and are high quality. I have personally bought items from this vendor and am very happy with quality and shipping.

www.zcarparts.com - they offer the 240z and 280zx kit. These kits do not place the engine as far back to the firewall as the one above, but require less modifications to car.

www.hybridz.org - v8 z car online community. Get information and inspiration for building your own v8z.

 

Don't forget www.brokenkitty.com for the original LS1 V8 conversion components.