Well if money is tight, you'd better forget about it....
125 x 400Ah Lifepo4 cells might get you over 400 miles, if you were to drive with a very light foot, but then again, in a heavy, un-aerodynamic vehicle such as a Hi-lux, still unlikely.
But this is ignoring the weight and size of such a battery, it would come in at about 1,787Kg!!!, I don't think even a Hi-lux will handle that. Also, they won't physically fit.
Then, do you want to spend Approx. £50,000 on the battery alone in your 13 year old work horse?!
A realistic range of about 80 to 100 miles can be achieved for about £10,800 worth of battery plus the cost of other conversion parts, anywhere between about £6,000 to £12,000 as a ball park.