I have two of those old Peaveys. I replaced the speakers in one, using MCM Electronics, discontinued Eminence Beta 10 knockoffs. The MCM speakers are 150 watts, and have outperformed the actual Beta 10's I have in every application I've used them in. The excursion exceeds the Betas. I got them for under $11 each and bought a bunch.
The one problem was that the speaker openings were slightly small for the MCM's. I had to enlarge them slightly, which wasn't easy with the non-removable baffle. The MCM's perform great...as efficient, much tighter with more power handling. I love them and this cabinet with them.
The MCM model number was 55-1740, and they aren't available anymore. Whether the current MCM 10's are similar (or even superior) I don't know. I've used the current MCM 12 and 15" cast frame woofers, and they both need midranges. They are however, efficient with incredible low end. The graph for the 12" though, shows more high end than they appear to have in my cabinets. I added sealed midrange speakers, crossed over at 800Hz.
There are specs here for the 1740...middle of the page http://www.mcmelectronics.com/conten.../section05.pdf
Here is one of their current speakers...a cast frame 100 watt 10" $20 http://www.mcmelectronics.com/produc...-2961-/55-2961
This is the stamped frame version (ignore the 8" mentioned in the description) It's 125 watts. $12.50 http://www.mcmelectronics.com/product/55-2951
Here's their 250 watt cast frame 10" 6.5mm Xmas $30 http://www.mcmelectronics.com/produc...0-60C0A02EE15B
Spec sheets are linked on the pages.
I wired the two 4X10's using the MCM 8 ohm speakers in parallel/series for an 8 ohm cabinet. The current MCM speakers are usually available in 4 ohms too, if a 4 ohm cabinet is desired.