It’s so great you’ve got him a bigger cage!
Smaller rescues are often run by volunteers so getting replies isn’t always quick. Keep calling them.
I don’t want this to come across as negative as you are doing an absolutely brilliant job - getting that degree upgrade is brilliant, but I’m afraid you could still struggle with the cage size and getting rescue approval for adoption.
Free roam is good but they would require a cage to meet their requirements for any time the piggies have to be locked in. Rescues set their own standard on cage sizing and often it’s larger than the RSPCA minimums.
Unfortunately a 120x60cm is too small for two boars to be locked into. Two boys need 180x60cm (150x60cm as a minimum). A reputable rescue wouldn’t allow a 120cm cage for two boys due to the fact that locking two boys into a cage of that size is likely to cause space related tension and consequently fights. It would be difficult to fit in enough resources (you need two of everything at least a body length apart for boars) and still have enough space to move past each other without having to get close into a 120 cage. For boars, lots of space is vital to keep them harmonious.
If you could consider getting him neutered and then having the six week post op wait to become safe then that
might help. A neutered boar/sow pair can get away with a slightly smaller cage. However, while a 120x60cm is considered RSPCA minimum size for a neutered boar/sow pair again, another rescue may not approve it and would be very likely to want 150x60cm as a minimum.
Please don’t be disheartened and definitely keep trying though. They may have some helpful suggestions.
https://www.theguineapigforum.co.uk/threads/guinea-pig-forum-recommended-rescues.196734/
Cage Size Guide
(Just so there isn’t confusion if you’re reading other areas of the forum, cage sizing for commercial cages is referred to in their cm measurement so yours is a 120 commercial cage. I know you mean 2x4 feet when you mentioned your cage but
If you see 2x4 or 2x5 mentioned elsewhere, then those are referring to c&c cages but not their measurements. A 2x4 means a c&c cage of 2 grids by 4 grids which measures 150x70cm)