Mingles, Finding a Table used such as the HW-19 MK-IV used would then more than likely need an entirely new Armboard fabricated ala third party as you suggest, and would need to be drilled for the Hadcock Arm-Armbase.
The Spindle to Pivot Distance is very very close to the AQ PT Arm's specs, and since the Hadcock's Mounting Shaft Diameter is very thin, only requiring a hole diameter of 3/8", it may be possible to superimpose the new Hadcock Arm Base over the existing hole, re-drill-tap holes for the Hadcock Arm Base, and possibly "hide" the existing hole from the previous AQ Arm Mounting Base? This is a big "maybe" though?
The Arm Board is a seperate piece on the better HW-19 Tables which possess the Steel Sub-Chassis, which attaches via screws to the Sub-Chassis. There were two version Armboards, one was the standard .500" thick, which was at the same height-level as the Acrylic Plinth, and then there was the Super Armboard, being 1.00" thick, and did sit higher than the Acrylic Plinth itself.
VPI's literature back in the day usually touted the thicker Super Armboard as a sonic upgrade to the table, but there was another reason for the "requirement" of the thicker Armboard.
That reason was, the MK-III Platter, and particularly, the MK-IV-TNT Platters were much thicker and were higher in height versus lesser HW-19 Platters, and thus needed the Super Armboard to better correctly attain correct VTA height with an Arm. Without going to a thicker Armboard, the other option would be a custom made spacer between Tonearm Mounting Base, and Armboard. Mark
The Spindle to Pivot Distance is very very close to the AQ PT Arm's specs, and since the Hadcock's Mounting Shaft Diameter is very thin, only requiring a hole diameter of 3/8", it may be possible to superimpose the new Hadcock Arm Base over the existing hole, re-drill-tap holes for the Hadcock Arm Base, and possibly "hide" the existing hole from the previous AQ Arm Mounting Base? This is a big "maybe" though?
The Arm Board is a seperate piece on the better HW-19 Tables which possess the Steel Sub-Chassis, which attaches via screws to the Sub-Chassis. There were two version Armboards, one was the standard .500" thick, which was at the same height-level as the Acrylic Plinth, and then there was the Super Armboard, being 1.00" thick, and did sit higher than the Acrylic Plinth itself.
VPI's literature back in the day usually touted the thicker Super Armboard as a sonic upgrade to the table, but there was another reason for the "requirement" of the thicker Armboard.
That reason was, the MK-III Platter, and particularly, the MK-IV-TNT Platters were much thicker and were higher in height versus lesser HW-19 Platters, and thus needed the Super Armboard to better correctly attain correct VTA height with an Arm. Without going to a thicker Armboard, the other option would be a custom made spacer between Tonearm Mounting Base, and Armboard. Mark