Outer Limits 4x4 Board

is it a big job to change a 4cyl petrol to a 4 cyl diesel? (hilux)
or is it just not worth the trouble and cost.
I'm thinking you would be best to buy a diesel from start.

doesnt sound that big compared to dropping an eight in something. but maybe the gearbox would need to be changed too........differnet gear ratios and shit