Well if you are intending for engine swap then i think you should get the cheap option in market which will be around 10 to 12 92-94 model. Then swap it with the 4.5liter petrol engine. Its costs around 3 lacks i guess. But other interesting and wild option will be getting 4.7 liter cygnus engine. You will need to replace the gear too.
About options there is cruise control dual ac cool box etc.
There are also already petrol models in market too which will costs aroun 14 to 18