A couple of easy and relatively low cost items would be AL manifold and water pump. Add aluminum heads and radiator. These help both overall weight and F/R balance.

I do believe rear battery is a good idea for balance.

Aluminum block would be really nice but spendy.

Lighter body panels (fenders, hood) would really help but expensive and may look funny.

On wheels, high end forged AL wheels in size of your choice can lighten things up but spendy.

Personally, I would not lighten up bumpers or brackets or door beams w/o cage for safety.