The guy that did the G10 swap is "fujioko". He's on here but hasn't been here in a long time. Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Profile: fujioko
He did a B3 swap from a Festiva on another Miata. The B3 is a de-bored version of the B6 in the Miata, SOHC 8 valve too. All the B series engines share a bell housing bolt pattern.
Festiva guys basically give away B3's.
Looks like he also swapped an RX7 5th gear in. Not sure how much difference.
BP+T/G5MR swapped '93 Festiva
Escort GT Block, Garrett T3 45trim, A/R .42/.48
---Bests with BP+T---
1/4 mile ET - 12.50
1/4 mile MPH - 111.5
Best MPG - 36.8
Average MPG - 31.6 (over 14,300 miles)