(If this is in the wrong section ? Please feel free to move it.)
I bought one of these recently , after using one to start the '57.
That's 454 cubes of Chevy V8. Started from 'flat' with no problem.
Halfords RRP £60 (they were on a 'Special' awhile back). Others on eBay
(Used / Recon, etc.)
Phaze 4 in 1 Jump Starter 12V 17Ah Portable Power USB Power Supply LED Work Lamp | eBay
Phaze 4 In 1 Jump Starter Booster 12V 17Ah 350 Amp 2000cc Petrol Diesel Engine | eBay