I'd be tempted to just convert your GE. You can run 400hp without changing anything. Gasket or head.
Injectors and a fuel pump with a fuel setup, map a fitted standalone and you're pretty much there.
You don't need anything from a GTE unless you want 500+, where using a head gasket is needed.
FFIM will help but its not essential. The one linked looks good. I'd be tempted to go all out and fit a drive by wire throttle. Or if you're on a budget use the original and extend the cable. Kit throttles can be hit and miss. I've had few issues over the years trying to use non oem ones.
GE vvti head does seem the way forward from many setups these days. I've bought two. Just in case