TCS has the best price on diffs, but you can get the whole bulkhead with the BP ones off ebay for about 35-40$.
I think 2028 will be way overkill for the Savage, 1717 would be enough but it's only 45k RPM.
Also check the Woodster 5T body, cheaper than PL and more durable:
http://www.davesmotors.com/s.nl/c.88...t.A/id.7855/.f
http://woodsterlidz.com/index.html