Gearbox:Best Option?

Its a 1975 FJ40. Just dropped a Holden 308 into her. Currently running a stock 4 speed, hence the need to go for a new box&tranny. Would love to stick with what i know, but i do alot of freeway work and need the overdrive!
Im really trying to determine the relative cost/risk of buying a reco'd combo which might pack it up next week vs reco'ing an already shot unit, which i could then be sure was right.
Thanks for the prompt reply.

Hi
If you already have the 4 speed in it, i wouldnt bother with a 5 speed...they are not that much overdriven...15% thats all, and all the tailshafts are different lengths. (this would be equivalent in 5th with std diffs to 4th with 3.7 ratios)
Marks 4wd make transfer gears that overdrive in high and under drive in low range......IMHO this is the best option...high speed diffs reduce crawling ability, as do bigger tyres, but bigger tyres make for better ground clearance, however, they need higher suspension....A 5 speed is a good idea if u can find a fj42 with complete 5 speed/shafts in it....for a good price.Another idea i had a while ago was to fit an 80 series 5 speed out of a 3f 1990-1992 80 series with the marks adapter bellhousing ring....that would make for a constant 4wd shorty with 2.45 low range, and no 5th gear problems :-)
Andrew

Have you thought about a 4 speed auto from a Commodore V8?

Rather than spending the money on a 5 speed (which has it's issues as already mentioned and a real pig to remove the 5th gear of the shaft when repairing - needs lots of heat and a good press).

Having had a 307 Chev in a shorty some years ago from memory it was about the same if not cheaper to buy a 4 speed auto - from a VP series Commodore as it has the manual valve body not electronic on the later VR onwards, plus the transfer case adapter kit than the 5 speed manual alone.

But I sold it before doing the change over, however "I" would go the auto option if I had the chance again. PS: don't forget about the disc brake upgrade too.