On ILS glidepath and stable at Vref +5 kts the difference between pilot eye height and the glideslope for the following aircraft is, according to company manuals;
B767-300 4 feet
B747-400 16 feet
The B767 glideslope antennas are behind the radome and on the B747-400 there are two sets of glideslope antennas, one set behind the radome which are used when the gear is up and another set on the nosegear doors for when the gear is down. The changeover is automatic and there is no noticeable flight deck effect when it occurs.
Company manuals also state not to use VASI indications below 300' HAT although the PAPI can be used until over the threshhold.
Regards,
BH.