I used the Z/28 spring on my 292 but I'm under .500 lift. The stock spring is capable of up to .450 lift..then the Z/28 up to .500 and there's the 470 capable of up to .600 I believe...been awhile since I looked in my power manual. For my machine shop to install the lumps I think the labor was under $100...so $165 for lumps and to have them put in....the total cost to do the head was around $800 including all the parts and labor. Think you could wait a tad longer to save up more money to add them in? The lumps make a big difference themselves.
