[BR3W CITY]

its the older truck head.
706 heads
Intake Valve Diameter: 1.89 inches
Exhaust Valve Diameter: 1.55 inches
Stock Head Flow Numbers
Chamber 61.15 cc----0.100--0.200--0.300-- 0.400--0.500---0.550---0.600
Intake 200 cc----------63 ---128----179-----210----218----221-----226
Exhaust 70 cc----------54 -- 93 ----121----145-----163----168----174

Not exactly the king of the hill when comparing flow numbers to other castings.
I have heard of people porting them, but for the cost and availability of other heads its probably not worth it.
IMO you can throw a turbo on anything you want. It might not like it quite as much as a 4" bore motor would, since the compression is higher, but with a good tune i see no reason why it wouldnt' work.
iirc there was a member here with a stockish 5.3 and a s400, i think it was a light blue truck but I can't remember his name.