Brother the tendency in our mechanics is that as they see the engine, they tell u that u r running a margalla engine. Basically japan have fixed this engine in both jimny, sierra, samurai, margalla and surely in many other cars around. So actually u were previously also running the jimny engine in yr sj 410 with it's original 5 fwd gear. The difference is that in margalla it's fixed side ways and in jimny they are fixed from front to rear.
Just change the engine g13 and make life easy for u. The fuel efficiency will be around 10km/ ltr on long. And the price of kabli 5 fwd gear will be around 30k. no exact idea about the engine, surely 1 lac plus.
Were u initially using an EFI or simple engine?