I only paid $2000 after shipping+machine work for my 418 forged short block. The DSS block is $2499, and after shipping, extra parts, etc., it'll probably be around $3000.
A friend of mine has the Mac headers on his 427W 95. He said they are a pain to install, but they will work.
I got my AFR 225's with all the upgrades for $1900, they were around $2200 new. I didn't look for anything else, but he said he will be using TW heads for it.
Yes there are plenty of cams out there, but you'll generally get the most power from a custom cam. My friend with the 427 has the TFS stage 3 in his, AFR 225's, and the spyder intake. My custom cam is very close to the TFS in lift, not sure about duration/LSA/etc. I'll let you know how mine compares to his when I get it running in a couple weeks.
I thought the EFI spyder intakes were around $600+ new from CHP? I paid $700 for my Vic5.8 with a little work done to it.
All the prices I listed are for brand new parts. If you wait for it, Im sure you can find some good deals on ebay or classified ad's.
Like I said, it can be done on a budget, but 540RWHP will be hard to achieve on a budget.