I think you’d make a great 4/8 runner with a bit more endurance development. Endurance training doesn’t look the same for a 4/8 guy as it would a 16/32 guy tho. Things like 4-5 300m repeats in 44-45 seconds with long rest and 6-8 400m repeats in 68-70 with shorter rest would give you a lot of bang for your buck in the endurance department, you don’t need to worry a lot about the tempo runs and long runs.
Id try to see if you could do something like training with the 400m crew, but doing a 5-6 mile easy-moderate run and one of those sessions once per week. A strong 4/8 guy is extremely valuable to a highschool program because youd be useful in the 400, 800, 4x4, 4x8, SMR, DMR, and maybe even 4x2, so I’m sure you could get your coach on board with it.