5.3 swap in 84 c10. tank question

Hey guys. As stated I have a 84 c10 regular cab short box swb truck. I have dual I believe 16 gallon tanks. Now I bought an 87 sending unit with ep381 pump and an 87 20 gallon tank. I noticed though that the 87 sending unit seems to fit into the 84 tank with no issue. Is there any reason I can't run the sending unit and in tank pump on the stock 84 tank? If that is the case then I will return the 20 gallon 87 tank that I bought. Thanks!

87 tank should have a baffle in it to keep the fuel around the pump.

I bought an 87 tank and sending unit for my 84 swap. Still working great. Fuel gauge doesn't bounce around like it used to with the 84 tank also. I have a small build thread in the pics and video section.