Yes, to a degree. But I don't think that will do what you are looking for.
If you properly tune the carb, then it shouldn't make that much difference in vacuum.
The camshaft has more influence on vacuum than carb size on engine vacuum. (Rhoades lifters can help that also).
If you want more MPG, increased vacuum, and improved throttle response, then order a set of Rhoades lifters part # 2018
Read the second article here to understand how they work:
http://www.rhoadslifters.com/Pages/Articles.html
You can get a set here:
http://www.summitracing.com/search?...tOrder=Ascending&keyword=rhoades lifters 2018
You should also be running a good dual plane intake manifold.
The best for your application would be to find a used Edelbrock LD4B if your 273 is 66 or 67. Edelbrock D4B for the 64 & 65 273 as it has the odd intake bolt angle for the older 273 heads. If not, find a good dual plane intake, not single plane.
You may get a small increase if you change carbs, but I don't think that is your solution. I feel you will get more of what you are looking for with MPG, increased vacuum, and throttle response with rhoades lifters. I've been running them for over 25 years and they work. I've ran a set over 250,000 miles on a daily driver. They bleed down at idle and take out about .025" lift and 15° duration, then "pump up" and give full lift and duration over 3500 RPM. It's like having an adjustable cam. You get your cake and eat it too. You will definitely get more manifold vacuum with rhoades lifters.
I built a 318 many years back with 10.5 compression, used stock 340 cam, Rhoades lifters, stock 318 heads and intake, stock exhaust manifolds, 2 1/4" dual exhaust, and a 2.76 gear in a 68 Barracuda daily driver. It idled at 24" hg, but had problems with detonation causing overheating in warm weather.
I swapped the stock 318 heads and 2 bbl for a set of 77 360 heads (1.88" valves), a 69 340 dual plane intake, and a Holley 600 vac secondary. My vacuum went from 24" to 22.5" at idle. That is with 9.2 compression, and larger port heads, I only lost 1.5" of vacuum at idle. That is also going from a 2 bbl to a 4 bbl. I don't think that the increased carb size (even from going from 2 bbl to 4 bbl) had as much affect on the idle vacuum as the compression and port size did.
With a 2.76 gear, I was getting 17.75 MPG on the highway.
Run a dual plane intake, get a set of Rhoades lifters, and then tune in your carb. I think that would be your best approach. Then if you wish, you may try another carb, but I would try tuning what you have before throwing it aside.