4-6 drop question

[Smokeater88]

I am new to lowering trucks all the suspension work I have done is to lift trucks for off road. I have a 72 chevy c-10 LWB. I have the bed off for body work and want to do a boyd tank between the frame rails any advise on what tank to buy (side fill top fill, any other parts needed, or modifications to make it fit)? and can I do a 4-6 drop with that tank. I have seen posts about guys with a 4-6 drop with out notching the frame. I am thinking about the ece kit unless someone knows a more budget friendly kit. This truck is just for cruising so I wont ever be loading the bed or towing. Any input will help I am very new to this.