727 4 pinion planetary....

hey guys, I know I have a few threads open on here right now, have a pile of stuff going on at once it seems. anyhow, I pulled my 727 apart last night because the casing has a few cracks in the bellhousing. plan is/was to remove all the guts and the output shaft and housing and discard the casing. I picked up a 73 rv 440 with the mated 727 which has the tail shaft with the bolt on yoke and support bearing. the plan is to gut the new transmission and swap out the tail shaft and housing, and rebuild one good one. however, I have no idea what the old 727 came out of I bought it for 50 bucks 4 years ago and put it though the stocks, upon disassembling I noticed that the rear band to be cast iron, and that the front planetary is a steel casing 4 pinion planetary, I looked at the clutch packs and such and they seem to be the standard duty 4 steel 4 friction setup and the springs in the rear drum I counted 9 out of the 15 possible, what throws me off really is the front planetary and the hd band.
the other reason I was picking up this other trans was I thought it would have had the beefed up components am I wrong in this thought? as far as the other trans i was told it came out of a cordoba any thoughts to what i have here? or is the 4 pinion planetary standard for the front and the rear is the one that needs to be beefed up? i can get numbers off the casing but have no idea where i would begin to look them up?
thanks