Transmission Gear selector issues

OK maybe someone on here might have an idea I have a 71 Duster originally had a 6 with 904 it now has a 360 with 727 from an 88 D250 in it. My issue is with the gear selector I'm having issues getting it adjusted right when we adjust it so when it shows the transmission is in revers neutral or drive that's what gear the trans is in but when you put it in park it's still in reverse. When you adjust it so It's in park every thing else in off neutral the trans is in reverse drive the trans is in neutral and D2 the trans is in drive we played with it for a couple hours with no luck.