hopefully this will help
1 silvertop turbo. check this out: this guy did it in a levin or a trueno i think, same thing really:
http://forums.toyspeed.org.nz/viewto...ilvertop+turbo
2 as above,
3 check this out: accurate specs for all 4AGE engines:
http://www.users.bigpond.com/vidore/...age_engine.htm
4 im damn sure anything 3e,4a,etc will bolt up with little or no modifications necessary.
Blacktops:
I'm running a blacktop 20v myself, keeping it strictly N/A though, thats what blacktops were designed for I.M.O.
Haven't seen these turbocharged yet, bear in mind that these have slightly higher compression than the silvertop/other 4AGE's and the standard rods are apparently weaker than those of the silvertop (rumour has it).
I.M.O your best choice would be the 4AGZE(supercharged variation) its a 16v rather than a 20v but the internals are better suited to taking on a turbo with far less modification than any N/A 4AGE.
hope this information is helpful.
gud luck with your rolla