Without spending an obscene amount of money for an oven is it possible to create one large enough for like a 16’ boat hull with high temps ranging 250-300 f?

If so what kind of things do I need? This area is not something I’m intimately familiar with.

I agree with everybody here.  SSR and PID controllers are great.  Circulating fans are key.  Fire-proof insides are a good idea.  It's still dangerous and you really have to be careful that stuff can't get sucked into the heaters.  And 120C is pushing the upper end of what is comfortable for a home-made oven...  I don't really see the advantage of curing low-temp pre-pregs above 90-100C given how hard it can be on tooling, CTE issues and problems with foam cores.  There are lots of good resin systems that work beautifully in this range.

Here's a post on making and buying ovens:  https://explorecomposites.com/articles/tools-and-equipment/oven-options-for-pre-preg-curing/

But really, be careful!  I have had oven heater fires (and close calls) and they're scary!

I did simple 4x4cm metal frame, insulated with 5cm alu sided panels, heated by 2kw industrial blow heater and cover everything with 25mm wood boards.......still runing cheap ebay PID controler trought SSR as i was only using it for infusion post cures (60 deg).

Dimensions are 200x100x90

Next step will be Omega PID and perhaps one more heating/blowing element if needed (tho i plan to use low cure cycle for prepegs).