Yes you can install Mod-Spdy on InterWorx please follow the instructions below:
wget -N https://dl-ssl.google.com/dl/linux/direct/mod-spdy-beta_current_x86_64.rpm <--- 64Bit
wget -N https://dl-ssl.google.com/dl/linux/direct/mod-spdy-beta_current_i386.rpm <--- 32Bit
yum install at
rpm -U mod-spdy-*.rpm
Any Mod Re-writes need replacing with:
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteCond %{SERVER_PORT} ^80$ [NC]
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}
On Blesta Installations:
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteCond %{SERVER_PORT} ^80$ [NC]
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI} [R=307,NE,L]