0) Use a regular old manual transmission with about the right ratios and leave it in 2nd or 3rd gear. There is something to be said for the old standby.
1) take that manual transmission with a helical gear ratio (not 1st gear, basically) near the 2.36 number, then remove all unneeded gear ratios and all the shifter components, and lock the remaining gears into position to make a single speed reduction. Ensure that the remaining moving parts dip into the oil sump for proper lubrication. you may need to fabricate spacers, lock rings, and such and/or weld parts together but with some expirementation it may be doable.
1.5) do the same thing with an automatic transmission. Probably harder than with the manual.
2) Use a synchronous belt and a pair of pulleys selected to give 2.3:1 reduction. I did this to get a 6:1 overall reduction (later changed to 4.8:1) using a 4.1:1 toyota diff. See relevant page on my website at http://amphibike.org/blog/scion-xb-ev/scion-xb-ev-construction/scion-xb-ev-drivetrain/
3) With certain differentials, you can change gear ratios, and some diffs will go to a pretty high ratio. Some ford and chevy rear ends in sizes found for 4x4s and such you can get an 8:1 diff ratio I believe. Would that be close enough? Could you make up the rest of the difference with a tire size change? As long as it is about the right size, a rear end swap on solid axle cars is not /that/ hard to do.
4) Go totally junkyard wars and take two 3:1 differentails, lock the spider gears in one, and use it to drive the second one to get 9:1 overall reduction. Might make an awkward drive arrangement though.