I never measured the bore on the first .45-70 I had success with in paper patching.  The first two paper-patch moulds I found were a Hoch 500 gr of 0.444" diameter and a Steve Brooks 540 gr of 0.441" diameter.

I cast and patched a bunch of these, checked the fit of the patched bullets in the muzzle of the rifle, and went on from there.  They didn't stick, or fall through without resistance, so I figured that was good for starters.  Later I reread Elmer Keith's instructions and pushed the things through from the breech and got the same results he got, so I guessed I was on the right track.

The Brooks bullet shot very well; the Hoch, despite the tighter fit, has never done as well.  I also had success with a Red River Rick mould of nominal 0.442" and eventually lapped out another Brooks mould (of nominal diameter 0.441+") to 0.443". This last is the one I use more than the others now, but I haven't seen any consistent accuracy differences that I can assign to diameters one to the other.  The RRR bullet shoots very well, but casting is more complicated because it's a hollow base adjustable, and more finicky to cast with.  The 0.443" also needs a little less of a squeeze with the mouth reducer, so that is the one I generally reach for first now.  Also, of course, once I put extra effort into something, I tend to use it more.  Just me, I guess.

But the point I was trying to make is that there is going to be enough cut-and-try experimenting (except for the fortunate few), regardless of book learning or advice on what is supposed to work best.  The OP himself posted because the plethora of "Thou Shalts" and "Thou Shalt Nots" understandably confused him as to which draconian requirements are more important than all the other (sometimes conflicting) absolute must-dos.  Having a point to start from beats any amount of preliminary measuring and figuring that might mean anything or nothing by the time the gun is loaded and fired.  Casting and patching a bullet that one already has the ability to make and seeing whether it actually rattles down that oversized bore or slides like it should (regardless of the measurements) would be a more definitive indication of whether the setup is likely to work than generating a bunch of numbers that may or may not be applicable, but do indicate (according to the authorities) that one needs to buy a whole bunch of extra stuff before a shot can be fired.

This gun has never been fire before. So I don't even have once fired brass! 
45-90 is not something I could get at my local Cabelas so I started researching how to make one and after many rabbit holes, I have arrived here 

The other option might be get one of the 535 gr money bullet grease groove bullets, some top notch bullett lube like Bullshop NASA or SPG and get a handle on load development and the mystics of match shooting.

Well good luck and have fun with it
Target rifle is a fun and challenging game to play
Keep us posted on your progress

Just to be clear. I haven't fired grease groove bullets in competition for over a decade, prefer to use patched.
My thoughts on suggesting the money bullet was only intended as an expedient manner for him to get prepared to attend a big match, a not very long time from now.

Probably wouldn't need to size the bullets from one of the BACO moulds. Just pan lube them.