Firstly Hello

- this is my first time posting and I am hoping that you Suzuki experts will be able to help me.
I have a 1994 Vitara with a 1.6 8v manual engine. I have owned it for almost a year now and it has never been a very happy little car - it has never really run quite right

. The car has also used a fair amount of water.
This weekend I decided that I needed to find out what was up with the wee girl. To cut a long dismantling story short I stripped the engine down to the head gasket

- I was hoping to find this at fault but I have discovered a nice crack between pistons 3 & 4

.
I have now decided that engine replacement is the only way forward

. I have also decided that I will take the girl off road and trailer her around to off-roading events.
So Why am I posting

? Well Any helpfully advice about engine replacement would be good - also I may look to put in a reconditioned one in if anyone can suggest a good place in the UK. But what I really need help with is I am thinking of putting a V6

in if I can sort it out. But do I need to change the gear box and diffs as well? Or are all of these compatible?
Sorry for the long post but its been a long weekend and I am looking for some good news about replacing the engine from someone!
Thanks for any help!
Cheers
Steven