I have a 305 and a friend gave me a deal ($100) on a stock Vortec short block out of a '97 Tahoe. Being that I am HP biased and like TPI (weird huh?) I have to admit I always found the 305 builds more interesting. The bottom line is I still think my 85 Z28 deserves the life it never got from GM which is to be a true performer so the 350 is most likely going in. Who has done the swap, how big was the difference?
Just so I dont get asked, I have never had a 350 TPI car. I have a few 305's, 1 350 carb 3rd gen, a 95 Z28 M6 and 98 TA 4L60E. I sold the TA for another third gen.

 

when you swap in the 350 you will need larger injectors (22 lbs) and a chip burned to run them. you will also choke out sooner with the 350 vs the 305 running a TPI.

 

Its almost exactly the same everything mounts up you may need to change the pulley system.

 

A Vortec short block?
Two options:
- You'll need L98 heads to bolt the TPI intake on.
- You can put the better flowing Vortec heads on but you'll have to redrill them to accept the TPI lower intake bolt pattern (not a bad job).

Might I suggest full-roller rockers while you're at it? One of the cheapest HP gains out there.
Well, since the intake is off anyway, why not put a better cam in there? LT4 Hot Cam for higher HP up top or the ZZ4 torque cam for more torque down low and better fuel economy.

Yes, you will see a noticeable difference, especially if you let the engine breathe with headers and decent exhaust. My 305->350 swap got me gains not only in power but in fuel economy as well (due to a more efficient engine configuration). I went from 18mpg to 25mpg.

And don't forget to buy wipes. Lots of 'em!
You'll need plenty to wipe the grin off your face afterwards!!

Lou

 

I think eldbrock makes a lower tpi vortec base.