1998 K1500 P/U VORTEC 5.7L TIMING 180 OUT AND RUNS?

Hello all,

I am currently rebuilding a 98 VORTEC 5.7L for my brother from another mother. As I was doing th tear down, I placed the timing mark on the harmonic balancer with the TDC mark on the block, and when I removed the distributor cap, the rotor was pointed to the #6 Cylinder, not #1. When I pulled the heads off I did notice that both the #1 Piston and #6 Piston were in a TDC configuration, when I removed the distributor from the block, to circle just below the cam gear was aligned with the white line mark on the shaft. But, again, the rotor is aimed at #6. The engine did run smoothly before this tear down. I am rebuilding it because it lost it’s rear main seal, and the a lot of the gaskets were leaking oil as well, so as a favor to him in this COVID-19 business, I am rebuilding it and all he is paying for is the parts. But for the life of me I have never know a 5.7 to be 180 degrees out and run smoothly? I do not have the timing cover off yet, and I know there has been work done on this engine in the past, is it possible the something in the crankshaft/cam shaft timing relationship is backwards or something? When I put the engine back together I should use TDC #1 Cylinder right?, I just don’t want it to throw a crank/cam correlation code after it is all build and fresh for him again.