After chugging at this for a week, I finally managed to make a decent volumetric explosion that can be raytraced and can cast shadows.
Used a build with soft ray shadows for this as SSS didn’t cut it. Main thing was textured planes and textured lamps
Only postpro I did was ugly noise removal in the Blender compositor and sharpening in a paint program (which could’ve also been done in the compositor). Lighting, texturing, and all that was done in BI. I say noise removal because the ray shadows would need a good amount of samples to avoid making parts of it very noisy, and that would increase render times.