Other than Mehran hmm
It's possible but its little tricky with Nissan Sunny 1990-95 & Mitsubishi Lancer 1990-95, which might be seems awkward when you think about old cars but its worth it when you have knowledge for mechanical/electrical. because 500k is the amount in which you can get this old car and set it like a new and trouble free car and better than mehran, cultus, passo. Vitz etc.. because small cars which have extreme high price in Pakistan.
First you have to find a non-accident car with good and clean interior and exterior then you have to go for swap once you done with swapping you'll be trouble free.
In Mithu Khan Ahata Rawalpindi you have plenty of options to swap engine/mechanical with automatic transmission or manual, parts and also electrical work of new engines. I have experience of swapping engine in Nissan and Mitsubishi and it make me satisfy it can be done in low budget. both engines can be set on bolt to bolt with their brands no need of any stupid alteration.
Its tricky but (full khwari program for two days at least :))) because when you swapping new EFI engine which is available in 1000cc. 1500cc & 1800cc but 1300cc is rare to find if you find it then you are lucky basically these are used engines but its just like a new, your electrician should be smart or pay him extra to set your engine on exact factory default settings by its computer then you can use car for more than 5 years without having any trouble. I am sharing my personal experience and there is no trouble since 5 years I am using Nissan Sunny B11 with (CG10, 1000cc EFI engine) and its fuel consumption is 15 to 14km/litre without any trouble, and both brands are much popular in Malaysia, Singapore, Thailand, Taiwan & Korea.
A person name Mushtaq who deals in Mitsubishi & Nissan engines/mechanical and he have good reputation in market.
Once again I must say its tricky but it is best solution to have car with new EFI engine and use it for more than 5 years.. as per your budget. You can see the attachment for reference.
Otherwise increase the budget and get what ever you want.
For more information you can contact me on 03324129788.