I would say you would want to spend at least 6k on an engine and then another 4-5k on an install. Sump, exhaust, tailshaft, transmission crossmember and front engine plate all have to be custom made. A stock 302 Cleveland will make the same power as an L28 but a bunch more torque. Spend 6 grand on one and you'll get something upwards of 400hp, for 12 grand you would be around the 500hp mark which would require a diff conversion and a strengthened chassis.
The first engine combo i had in made 157 RWHP and was good for a mid 13 second quarter. I have installed a stand in engine with more internal mods that is a lot stronger, i did this to pull the block out that it was engineered with to build a 393 stroker that is Nitrous capable.
I just renamed the thread to make it easier to find
http://www.viczcar.com/forum/index.php/topic,11096.msg111749.html#msg111749
And there's the facebook page which has a lot more photographic content
https://www.facebook.com/PNK260
I would say the main problem for an S30 is you may be restricted to a lower cubic inch but that would require a calculation based on the vehicles weight to what size engine you can fit.
My business page is below.
https://www.facebook.com/StreetWeaponRestorations
I will see if i can get the new engine combo on the dyno in the next few weeks and see what it's pulling, fuel economy is around 25 litres per 100 Kilometers city cycle with an auto (same as a H2 Hummer )