That place is a general idea of what you can have done for a fraction of the price of new injectors.
Okay, h.o cams will work with stock springs. I'm sure h.o. springs would be better.
As for heads, yes standard heads will be fine with those cams.
I know of a place that sells heads for $500 a stock set. Ill look for the number for you. Also I can get ported heads for around $8-$900.
Text me if your interested 979-645-0330