A 410 should do 70, yes it will be screaming but trust me the engine can handle it! I once got 73mph (gps) with mine on 30" tyres. fitting a 5 speed is nice and easy, it has to be a 410 5speed though as the 413 has a bigger bellhousing and wont fit. It shouldn't take longer than an hour to fit either, I can change a clutch on my own in under an hour

For what it's worth though there isn't that much difference, you need to be doing 50mph to be able to accelerate in 5th if you run 30" tyres, it will trundle around at 30 in 5th but dont expect it to move when you put your foot down

I must admit it was better for dual carriageways, big A-roads and motorways though. well until you got to even the slightest of hills that is
