200 or 221. Which one Do I Build

I plan on building an engine for my XM later this year. I was planning to build a 200.
I have a freshly bored & decked block, new pistons (.060) new bearings, arp stud kit, cam & chain.
What my dilemma is, that I discovered I have a 221 bottom end in the shed (I have a lot of stuff in my shed)
After doing some reading here I realise there are a few questions regarding parts swapping
The 200 is out of an XR
Mains bearings. I have read that the 200 diameter is 2.2486 & the 221 is 2.3986. Is this so or is the smaller measurement the US 200?
Timing chain length. 200 uses 25 link chain. 221 uses 26 link. Is this the same as the XY-XB 250?
Pushrod length. Anyone got the measurement for 221 rods
Crank Snout. Getting mixed messages here. I assume the snout is the same from XK thru to XB, seeing as I just put an XY balancer on a XP 170
Cam bearings - Are these the same. If I cant use my new cam I think it will be the dealbreaker.
Flywheel PCD. Seems to be the same. My car is auto, with the flexplate from a wide block XP 170
Apart from the obvious weight difference & slightly taller deck height is there anything else that may trip me up.
Head will be 2V ported, cc'd, new valves, roller tip rockers etc etc

As far as I know all sixes from xk thru to xw had same mains and big end diameters, i cant tell you what the pushrod length is but Id say if you add the difference between 200 and 221 block hight to 200 pushrod length, then that would your dimension. As to camshafts then Id say try fitting the cam into the 221 block and check that the big ends will clear, Im fairly sure the 221 cam should have clearance "dips
in it to allow the bigend to swing past, you need to time the cam to check as the dips are stategicly placed. cam journals are all the same as far as I know.
Flywheel falnges is the same untill XY then goes to V8 flange.
I thought cranks snouts are all the same. Your xr 200 is seven mains?
221 with 2v head and a 350 holley works very well, Ive done a couple, and a couple with 250s and a 188 as well.
You dont need roller rockers in my view, save your money for something else.
BTW im building an XP ute with superchargded 200 crossflow on LPG, still in early stages, Ive done a 250, 289 and 302 into xps with C4 borg warner and top loader. Ive used 8 inch and BW diffs.
Hope this helps
A7M