So I ordered the more expensive route today. I feel more comfortable paying more and making sure I have the best and safest possible solution. And just to sum it all up to make it easier for others, I'll list what and how I ordered.
2 - "74mm-72.56mm" centering rings (called Ben at 877 533 8473 ext 660 from tire rack and ordered two just in case 1 breaks) at $6.00 plus $6.66 shipping = $12.66
1 - T145/70R-18 Bridgestone Tempa Spare LL tire (called tire rack again since not listed on their web site) at $277 plus $16.07 shipping = $293.07
1 - BMW 36-11-6-768-861 rim (ordered from
http://www.worldimpex.com/parts/bmw-...c_1533872.html) at $88.68 plus $20.08 shipping = $108.76
4 - BMW 36-12-1-116-326 rubber valve stem (Called Worldimpex at 800-736-3550 and they combined the order with the rim so I didn't have to pay additional shipping charges, saved $10) at $2.85 plus $0 shipping = $2.85
Total cost of $417.34.
Next step is to bring to my local tire dealer to get it all assembled.
Thanks to everyone who has participated in this thread. You all helped me come to my decision on going the more expensive route as well as provide great insight. And special thanks to Tom Tarzian and GregW / Oregon. Without you guys, most of us wouldn't even have this option!