Not sure I would bother with that.
If you are patient enough you can probably get an FA/F 50mm in 1.4 or 1.7 for 250 or 300 here in the marketplace. It's a couple extra dollars, but you'll save that money because you won't have the hassle and headache of getting rid of the equipment you really don't want.
Or, if you really want the A version of the lens instead of an autofocus version buy it for $150 at KEH:
Pentax Manual Focus 50 F1.4 SMC A (49) 35MM SLR MANUAL FOCUS STANDARD ANGLE LENS - KEH.com
- Sam
(I have done exactly what you are thinking: bought a whole bunch of stuff just to get a 50/1.4 and guess what ... I've not yet overcome my laziness and still have a bunch of gear lying around that I never sold off)