I want to move my battery into my boot and i have been thinking about just using 750amp jumper leads. will this work?

also what is the biggest battery i can buy( power wise) that will still be able to be charged by the standard alternator?

Take the existing battery out of the car, connect one end of the jump leads to the battery and the other to the battery terminals in the car (being careful not to let them earth) and try to start the car. That'll tell you if they'll work.

You could also measure the voltage across the battery with the engine running to see if the system will charge properly.

find out what AMP your starter motor needs and use welding lead and good crimps and the like Fit a bigger alternator? off a later modal Ford Cortina" the one with 3 bolt holding it together and rotate it round 1/3 of a turn and it will fit on the other side of the Escort motor -----some of those alternator are 60 AMP---

Welding cable is wot u need. As for battery make sure the CCA rating is up there...just fitted a 530CCA battery for 11.1 engine and it now starts easily with hi torque starter as well.