1971 K20 Gearing Query

[NZBurb]

Hi everyone.

Firstly thank you for the great active community here - I've learned a bunch from the numerous threads.

I've recently imported a 71 K20 (3 speed auto with a 350 GM Goodwrench) to New Zealand and now we've got through compliance we're finally on the road! I'll get some shots for you guys shortly :-)

Overall she drives really well, however at 60mph on the motorway she's really working at around 3,000 rpm. I'm currently running some 33s which leads to a gear ratio of 4.9 which seems quite high compared to the 4.1 I understand they were built with (dodgy tach?). She previously had 37.5s (I had to swap them out for compliance and didn't drive her with them on), so am looking for some advice on which would be the best option to work through:

1. Change the gear ratio (keen to hear what you guys are running)

2. Look at a new trans, e.g. 700r4 (keen to hear if there are any major challenges to keep an eye out for).

Thanks in advance for your hel[p,
Vaughan