More Tour Pack, Less of The Same

[stormi1237]

Howdy Y'all. I've been reading these threads for quite some time, figured it's time I joined in. Thanx for the useful knowledge.
Been riding a 98 flhtpi since last Aug. Love the bike... mostly the seat! Before that, 23 years on an 83 goldwing. T-boned by a cellphoner, no more wing. I've always loved the police bikes, I got lucky and happened on a good deal.
Here's my problem.... No rear box or rack when I bought the bike. (like to travel, need the room) Picked up the standard pd set up without the top plate figuring I'd mount a tourpack to it. Picked up an older tour pack (late 70's). Police size, 16"w x 20"L. Shouldn't be a problem with the saddlebag lids clearing, from what I understand. The tour pack has "spring loaded" mounting hardware on the bottom(pictured) that I'd like to use for quick connect. So here's the question(s)...
Does anyone know what rack these packs originally mounted on, I think I have an idea... 3 channel chrome?
And, will an older rack like that fit on a 98 E.G.? I wouldn't mind doing some modifying if it's possible. (I remember reading, with enough time and money, anything's possible) I got the time.
Thanx