Keep it #'s matching or swap?

[1970Turtle]

Have a stock 307 in my 70, should I leave it in there and make it just a little more powerful and keep the car #'s matching or replace it with a 350 but keep the 307? I keep hearing not to waste my money or time on the 307 I'm definitely taking the powerglide out and putting a 3 speed in since i'm using it as a daily driver. What's everyone opinions?