The Icom IC-756pro3 has 2 options for tapping the IF, one is at 64.455MHz and the other is at 13.345MHz taken from the bands scope circuit. This article covers tapping the IF at 64.455MHz which I found more useful for using with an original FunCube dongle and an RTLSDR dongle, both of which work from about 60MHz up.
After removing the bottom cover the RF sections are visible, specifically the RF-B unit.
I found on the RF-B board of the IC-756pro3 there is a 64.455MHz IF test point, J1651 which was fitted with a Taiko Denki (TD) connector ideal for use a a connection point.
From the service manual;
I didn’t have an RF lead with a Taiko Denki (TD) connector on it so I just soldered onto C1651 next to the connector.
I opted to drill a hole and fit a phone connector on the back panel, while not an RF connector it’s suitable for an RX only connection for IF.