You need not swap the engine. The law states any vehicle which is used commercially and is above 15 years can't run on the streets of Delhi. It doesn't say private owned cars which have crossed 15 years cannot ply on the streets of Delhi. So chill there is hope. Now for the next part of the question I haven't gone for engine swap neither will I recommend that unless you are so mad about this car that you don't mind spending the cost of euro4 hatch. Yes if you have to plonk a safari engine and gearbox with wiring and ecu it will cost you close to 3.5 lacs parts Labour would be extra, this is if u want a new engine and gearbox. However if u are linking an engine from the scrap market it will not be deemed as car which has had a transplant it would be still be considered as 15 year old vehicle only. So unless you want to get it done from TASS where it will cost you a leg and a kidney to get it done( here I'm judging by my pocket standards) please don't get offended.i have left my sierra as is. I had renewed by RC is 2013 where I had got the RC valid till 2018 so I'm waiting till then keep it as is as in keep it mechanically and structurally. And if you get further extension on the RC it's fine or else I'll keep this car for my field runs. So even if you have renewed the RC don't sweat it restore it to the stock spec. If not just get it up and running enjoy the drive. I hope I have answered your questions and if you do restore it. Club Sierra India is planning a national meet and drive to Leh in 2018 in their respective sierras.