Buy an iron 5.3. Slot in some arp hardware incase down the track you want to boost it. 600ish rwhp with chinese turbo and intercooler, flipped truck manifolds.
I have a thread over in imports about importing and someone gave me the details of a really cheap guy. Think it was about $250 for a motor crate incl fees. You just pay the gst.
Get the LS mounts from TCI to suit your clip.
You can pick up a 5.3 complete with auto for bugger all. Around $1000 if you shop around. I think they are about 2k on ebay.
67 SS Nova Coupe. Iron AES LS. T56. Boost. TCI Pro Touring F&R Clip. Streetfighter Project. 1000rwhp or bust.
68 C20 LWB. Bagged daily. Bulk scraps.