Ok, I'm going to add my 2 bits worth here. You mention this is a project for your son (14) and its only going to be a lightweight car.
Had you considered using the stock vauxhall frontend and adding a decent set of aftermarket gas shocks (dampers) and look into a brake upgrade to suit - you may be able to achieve this by either a bearing change to allow using a larger hub/disc rotor or possibly use the vauxhall front hub and adapt on a 'Hat' type disc rotor (slip over style as fitted to a lot of Japanese vehicles '80s - '90s)
and then fabricate caliper mounts and add calipers to suit.
I suggest this option for a few reasons, the vauxhall front end is not a BAD design ( here in NZ there were many vauxhall vivas repowered with SBC using stock front ends) this would save you having to adapt in a complete front end swap, keep the track basically stock and hopefully keep the project on budget.

p.s. Vauxhall viva is essentially a firenza .