I think that the 16v will be a good choice.
well you can get a red top crate motor for around 560 on ebay or i would just search around on the web. There are a few places up here in washington next to me that have then but im not sure if they ship or not.
Just letting you know that a 16v can be just as good as a 20v with a little porting to increase head flow and then some cams. 16v is a great motor to build off of weather you are going turbo or n/a.