Well i'll answer one by one as good as possible.
1. No wheel arches protrude inside the cabin and there is no height at the rear. , safari rear seats could not be placed. but the wheel arches inside could be cut and brought down lower and the regular seat could be removed and new one fabricated - kind of one hell job , do it only if you want that badly.
2.i hope turbos's were sold some where near 5.8L and some on premium as the demand grew more for sierras. may be 50 to 80k less for std version? - not sure its all by word of mouth.
3.You are asking me to summarize this thread. Well mod in the sense , i have placed a electric fan for radiator by removing the mechanical fan making MY sierra quiet and for ac , the whole system is replaced by superking blower set up. And mine has a 16 inch wheel and tyres.
replaced the 65 amps alternator with 90 amps alternator.
4. No idea why you asked my odo reading. its 156550kms last Tuesday when it went for wheel aligning. i believed it may be tampered by previous owners
but given the engine condition now - i believe it must be true. the engine is still young and pull perfectly.
5.If you maintain your ride , there will not be single break down.
yeah there were timing belt issues with sierra. i replaced a year back. i was advised to replace at 40k kms by a old gentle man who did one in past. but i remember the manual had 36000 kms. it was a scanned copy of manual available in net. let me check and confirm . And i hope turbo's beld dont snap as the early std belts.
6.Oil filters , engine and gear box are same as tcic safari. the later gen gear box in safari as well as the dicor are exact match for this engine.
Except the pulley's ,fan shrouds and housing , ac - compressor[nt sure] and alternator
almost everything is same till the propeller shaft!
alternator was 65 amps in sierra , 120 amps in safari.
Suspensions are totally different.
sierra front suspension set up is exactly same as tata sumo.
rear is sierra specific , but the parts are still available.
Check this same thread , i have replaced all rear bushes.
safari was heavy weight for this engine - this is where sierra scores over and safari has a super real comfort .