Gday
I have an 89 runner and after exhaustive research i rebuilt my standard motor. It got a new webber carby but it only lasted 2hrs bench time, as i then decided to go efi. I did a carby job on my mates 87runner (my webber change over) and he is impressed with the fuel economy and the extra grunt at the rear wheels.
The engine overhaul depends on mainly funds, and as it is primarily a farm vehical you do not need all the extra goodies. Keep away from v6 conversions as you will need to replace the gear box, your G52 box doesn't have the guts for a holden v6 which a lot of people tend to do.
I have been building mine for 3yrs and it has "ALL" the best goodies money can buy, but it is still one very hot 4y which produces in excess of 130bhp.
If yours has low compression in number 2cylinder you have a very tired motor
A) you will need to rebore and go oversize,
B) rebuild your bottem end.
C) rebuild your head being as you can't do one without doing the other, as some thing will BREAK rule number #1 (if you do the top you do the bottom, if you do the bottom you do the top)
A rebuilt 4y will set you back about $1500 out of the create, mine was a lot more because it is a custom build. A "NEW" webber is about $500, this is just off memory. There are short cuts you can take that are a lot cheaper but they are dependant on vehical use, ie "just farm work", "into the local town", if you do highway driving and hard 4x4 work don't do any short cuts, it will cost you in reliability and funds big time.
I can post some pic's and more detail if you are interested, or just pm me.