Honestly, I didn't notice much change when I switched from 4.11 back to 3.70 on my TR3. I think with a stock engine and flywheel, the difference would be even less. The main thing I noticed was less of a tendency to spin the rear tires when turning from a stop sign. Which at least for me was a Good Thing as I don't need any more "unsafe start" tickets!
When Steve Hedke was preparing Scrappy for The Great Race, he did a lot of careful measurements of acceleration times under "real world" conditions. He reported finding that Scrappy was actually faster with 3.45 gears!
My opinion, you'll get more "bang for the buck" installing a lightweight flywheel instead of 4.10 gears. And it won't increase fuel consumption or engine wear either. Or lower top speed. Joe Alexander sells a nice lightweight steel flywheel that should be safer and more rugged than going all the way to aluminum.
However, it normally isn't drilled for the early clutch, so you'll need to either get it modified (I believe Joe can have this done when you buy it) or convert to the later clutch (which is also lighter).
I'm actually in the midst of building an axle with 3.45 gears and a limited slip diff; if I can ever get all the other chores out of the way.
PS, Joe's flywheel also requires the post-50K starter. If you have an early transmission without the extra bulge, a gear drive starter will still fit. Ok, so now it's probably more money than the 4.10 gears, but I still think it's better. I've been running a Fidanza aluminum flywheel for a lot of years and I really like the difference. 4.10 without OD was so bad that I risked not making TRfest 2009 (my goal in building the TR3) in order to take it back apart and install OD.