The SAMMI Specs for pressures are actually equal for all practical purposes in standard pressure ACP rounds (not plus P) and .45 Colt ammo.
In order for the .45 ACP ammo to work in that gun, a new cylinder would have to be fitted. There isn't enough space between the cylinder face and the recoil shield for the clips and case heads to fit.
On top of that, on an older gun such as this, the barrel is probably somewhere between .452 and .455" (maybe larger) and the .45 ACP bullet is typically .451" for jacketed and .452" for lead.
It is possible to find "remanufactured" ammo for some calibers, but I'm not sure about .45 Colt. If you can locate some of that, it will be cheaper than the factory Big 3 stuff. Gun shows are the most likely bet for that.
Dies are not that much more expensive than a box of Win., Rem, or Fed. ammo. Add a shellholder, use the same powder as for .45 ACP (if applicable--Unique, 231, and HS-6 all give me good results in .45 Colt), buy some cheap lead bullets and you're in business, loading a year or two's supply in an hour or so. My .45 Colt brass has been through about 12 loadings and is still okay.
Hope this helps.
[This message has been edited by Rod WMG (edited November 16, 1999).]