Well, you're gonna have to have a new driveshaft probably...but the first thing to check is the input shaft. A small block needs a small input (1-1/16 Diameter) and a long pilot (1.125").
For further reference, go here:
www.4speedtoploaders.com
Then click on ID charts...and you can get all the info you ever need.
I just checked, and the HEH-CL was in a 390GT Fairlane. More than likely the input shaft will not work with your 351W. The reason being, the input shaft pilot (the little stubby thing on the very end) is too short...probably around .75". This is not long enough to fully engage the pilot bearing/bushing in the end of the crankshaft, and will probably prematurely cause lots of problems.
That's a wide ratio 28 spline tranny....which would be fine for your application, assuming everything inside is cherry.
You might wanna look again at that tailhousing ID. David Kee's website doesn't have a listing for a C5 tailhousing. Does it match the tranny? For instance, mainshafts (the shaft sticking out of the back of the tranny) come in 24, 25, and 27" lengths...you have to have the appropriate tailhousing to fit it. My guess from looking at his website is that you need a 14" tailhousing (fits a 24" mainshaft).
I believe you could use a longer shaft and tailhousing....you would just have to shorten your driveshaft which you'll probably have to do anyway...and you'll have to find the appropriate shifter bracket that mounts on the tailhousing to get the shifter in the right spot in the floor.
Lastly, the bellhousing is for an FE big block...it won't fit your small block. You'll have to get rid of it.
So basically this is the parts you'll need now:
1. A bellhousing
2. A small block input shaft
3. You need to check on what tailhousing you for sure have
4. Shifter plate and rods to stick the shifter in the right spot.