3.07 diff vs O/D box

[Paul bow]

Looking for a bit of knowledge here guys..
Annoyingly I had my diff rebuilt and did not change the ratio, being a USA car it runs 3.54. Great fun but not so much on a motorway, so this winter I’ve a dilemma, do I change the ratio to a 3.07 and may be do a little work on the head to give a bit more power to compensate the slower initial drive or remove the engine and box and put an OD unit on it.. I’m not in the market of 7/8k 5 speed box’s unfortunately.. anyone views would be gratefully received.
Many thanks

[abowie]

do I change the ratio to a 3.07

That's a good start.

I have a 4.2 S1 car with a 3.07 diff and it is fine given that I'm limited to 100kph here.

[mgcjag]

If its for your ots you will struggle to fit an o/d without butchering the car..read up about 2.88 diff.....Steve

[abowie]

If its for your ots you will struggle to fit an o/d without butchering the car..read up about 2.88 diff.....Steve

It's a 2+2.

[mgcjag]

Ah yes the ots was previous.....lots of info on the forum if you search 5 speed options...once you get to 70mph on a 3.07 you will probably have liked another gear..you cannot add an o/d you will need another box with o/d..Steve

[lowact]

I'm doing both, 3.07 and O/D. From 3.54 (S3)

[Paul bow]

Ok.. so def start with the 3.07 and being a 2+2 prob do the Gbox as well with the compact OD unit, yes that actually sounds like a winning formula, with the exception of having to drop the engine out .. but at least it’ll be an excuse to get the spanner’s out again whilst it’s hauled up in winter.. cheers guys