altering a modded biome worldgen

hi, im new to datapacks, and while ive been trying for a while, i feel like ive been beating my head against worldgen and only making progress by accident, so im trying a new tactic. 
my goal is to make a new dimension that consists entirely of the 'visceral heap' biome from biomesoplenty, with the netherack replaced with the flesh block from biomancy, and the lava replaced with the acid from the same mod.
so far i am able to either replace the blocks but with vanilla nether waste generation, or make the correct biome, but with none of the replacements. 
i do not know where to go from here, or if what i want is even possible with these tools.