Hi Goliat6288: The entire engine assembly would need to rotated all at once, with all the gears and chains moving with it. If you roll it w/o some of the pieces it is recoverable but a PITA. From your description on the drawing post, I think 180 degrees out is likely---happily, an easy issue to fix---rotate.
The only V8's I've torn down were not OHC's so I am not the expert, but one of the first steps in an engine mechanical analysis is to find true TDC. It's where you want your motor to be before any timing parts are removed for sure. Now be sure the spark plugs are out to make it easier to rotate too. I have also used a pair of ty-raps-one pushed into the other to make a "T" to stick in the #1 hole so I can watch it rise with the piston.
I see on an quickee search that a few YouTube video's claim to show how to change the timing chains on that engine. I use YouTube video's a lot but never just one, I view several to get as clear a picture in my mind as I can. The drawing you posted is excellent BTW, a good thing to have.
Now engines do "Jump Time" with stretched chains, but they usually run so horribly that you wouldn't try to drive them. But with 2 cams, maybe just one jumped a notch so it could just be running rough, I dunno.
One more critical test for engine mechanicals is the Compression Check. Done with the spark plugs all out, throttle wide open (on newer cars that may mean propping open the intake however you can---let all the air in possible to get a good reading. I've heard from a few good mechanics over the years that the first two things they do when they get an engine in that's running poorly is the timing check and the compression test. If those two don't check out, no amount of ignition or fuel parts or adjustments will save the day. Some also swear by a "Leak-down Test" too, but that's probably unnecessary here.
One last thing: You say you're changing the Timing Chains---are you also changing the gears? Worn chains could mean worn gears too. Inspect them closely if you're leaving them. Worn gears get a "Hooked" shape to them and a new chain will wear extra fast and not really be properly tight on a warn gear. Bravo on tackling a tough job, perseverance counts.