4.0 bottom end interchange

my 2001 XJ has developed a knock from somewhere in the bottom end. it still runs perfectly, but there is definitely a serious mechanical problem inside. i have access to a good running 4.0 from a 94 XJ. i know it won't directly interchange, but i was wondering if the bottom ends are the same. can i just take the head and all electronics off the 01 and throw them onto the 94 block? i know the head will bolt up, i just have a few concerns:

1) will the shape of the 94 pistons match up with the heads and not cause interference?
2) will the 01 cam position sensor drop into place of the 94 distributor?
3) will the cam profile in the 94 be close enough to the 01 that it will still run well (i don't want to change the cam if i don't have to)?

is it just a knock at idle or it continue to knock as rpms go up?

knock at idle is somewhat normal but if it increases with rpms, i would rule out loose flexplate bolts or cracked flexplate.

my first thought (or hope) was that it was a loose torque converter, but it was all tight down there. it really sounds like it's coming from the dead center of the engine. it makes the sound at idle and when revved up. it's loud enough that you can hear it inside the car driving 40 mph. same sound all the time, just more rapid as you rev it up.

I'd dump the 0310 head while you're at it. Mine is cracked like so many others.

i'm just trying to keep it on the road cheap. has anyone done this before?

In theory, you should be able to swap everything.

ALL AMC "Modern Era" Six (199/232/242/258) cranks will physically swap. All of the 242ci pistons are functionally identical (later ones have graphite-coated skirts to help prevent scuffing, I think that started around 1994 or so.) All of the con rods are the same length (6.125", IIRC.)

The cam profile may be slightly different, but it should not cause trouble (I think it's close enough that OBD-II won't think anything is amiss, but I won't swear to it.) The heads will physically swap, but there are a couple of small issues that will want resolution - matching up exhaust ports and mounting the COP/DIS coil rail come to mind (information on both is around here somewhere.)

The "cam sensor/oil pump drive" is little more than a "headless" distributor anyhow, so it should drop right in.