What transmission to change to???

[1969chevy]

First post on here. I am starting to work on my project (69 chevy C10 lwb truck) after it has set for about 6 years now while I was in college and starting to work. The engine blew a rod and didn't have the money or resources to fix it then. I am rebuilding the engine now and am thinking about changing the transmission that is in it. It now has a powerglide transmission and am thinking about putting a 700r4 in. The problem I have with the powerglide is the high gear. When I was running 65 down the road the engine was running a high RPM's. Do any of you guys on this board have any suggestions/advice? I will be posting some pics and starting a build thread when I'm done with the engine. Thanks.