I understand that its a relatively simple operation to latch on a turbo onto the 2B or 3B engines and should cost around 6-10K depending on which turbo. Have never seen one but know that it is doable..
Upside: There should be a significant improvement in performance and possibly fuel efficiency as well. The AXT turbo website gives you dyno charts claiming that their 3B turbo would outperform a 13B-T http://www.axtturbo.com.au/toy3B.html
Downside: I am told that the life of the engine would be compromised as the standard pistons are not really configured to take the additional load. Also understand once installed, it is difficult to take the turbo off and will cost you more. Also I would think that that you would have to be very careful with temperature issues as you may overheat your engine if things are not working 100%.
Alt Views: There are a gazillion stories of people slapping on turbos on petrol and diesel engines which seem to run well... though this is not so popular in Pakistan....Note: AXT which is a credible Australian company sell a host of custom TurboKits for standard diesel engines of all makes. These kits sell north of US$2,000 and are quite popular it seems. See website: http://www.axtturbo.com.au/Turbos.html.
My Bottomline: I would not replace 3B with a 13BT but rather go all out for a 1HZ or 1HD... If i was in the mood for a panga project I would take the risk of installing the turbo as long as I could afford replacing/upgrading the engine if things go wrong....if my pocket was not deep enough and i was the age that I am now, I would sit back and enjoy the 2B/3B....its a great engine for what it is!!
Hope that helps...but if you still have an itch do speak to Master Mechanic Farooq Awan who has some experience in this territory. His number is 0333-5207251.