Help with oil pressure sending unit?

Hi all, new to the board, please forgive me if this topic has been covered...didn't see it in an hour or two of surfing prior threads, though.
My '88 2.9L started in with some serious lifter noise and slight power loss while coming home from work on New Year' Day. Nothing's open and I figure a wrecker would cost me a week's pay on the holiday, so I pulled off the freeway and into a parking lot to ponder my choices. Called my wife, asked her to come get me and poked around under the hood for a bit. Oil level on dipstick is full, no sign of water or antifreeze on stick or under cap, temperature normal. Definitely top end noise from the front of both sides. Don't have an oil pressure gauge, just the light. For about two weeks prior to this the oil light would flicker occasionally at a stop light with the auto tranny in gear, but the idle is about 100 rpm low and in park or neutral the light doesn't come on at all, so I didn't worry too much about it. Anyway, I didn't want to leave it where I sat, bed and cab FULL of tools. So I decided to fire it up after about 20 minutes and nurse it another half mile on the service road to a Wal-Mart lot, where at least there'd be lights. So I limped on over to Wally World and arrived at the same time my wife did. Noticed all of a sudden that I wasn't hearing any valve clatter, so I popped the hood to double check my deaf ears. Sure enough, barely a tick. So I drove it home. SLOWLY. Next day, I drained the oil to have a good look at it, looked a little dirty(2000 miles since last change), but no sign of water or glycol. Spun on a new Motorcraft filter and filled 'er up with Valvoline petroleum 10W-30 and fired it up. Hardly a sound, but when I run the revs up to 1500 or 2000 for 10 or 15 seconds, the clatter returns. Idle it for a while, and it diminishes almost to nothing. Don't know if this is relevant, but last oil change(2000mi ago) I added a quart of crankcase flush and idled it for 10 minutes before I drained the pan.
I figure oil pressure or delivery problem, but I'd like to know more, ie, what is the oil pressure like at cold start, warm idle, warm fast idle, etc. I fabicated a pressure tester from a 1/4" MPT fitting, some hose, and a 0-60 psi bourdon tube gauge since the local Auto Zone and O'reilly stores didn't have a tester to sell me.
So here I am ready to diagnose this thing and I'll be darned if I can get the sending unit out...it is sandwiched between a boss off the engine block and the motor mount plate. Can't get a socket on it because of the mm plate and a box end wrench or open end won't make the squeeze either. Took off the A/C compressor and power steering pump and mounting plate today to try and get at it from above. Still no luck. Hate to beat it out with a long chisel and BFH for fear of snapping it off in the block. Looks like a 1 1/16", but I haven't been able to get anything on it to tell for sure. I know it may well be crank bearing problems, but I'd sure like to quantify the oil pressures before I jump to conclusions. Can anyone offer me any advice for getting the sending unit out without lifting the motor? Sorry for the long post, but I didn't want to leave anything out.

SD

anybody have an idea?..I'm at a loss.

you might be able to turn the boss enough to get a wrench on it. It just threads into the block. If you can't do that you might have to support the engine by an engine hoist and remove the engine mount bracket for access.

Yes it is snug in that location...+1 as Holyford86 mentioned you "usually" can get it turned on the extention out of the block, such that a wrench can fit on enough to get to it better. The sending unit threads into the extention at an angle.... you'll probably have to angle the wrench a bit....with some patience you'll get it.

how many miles on your unit/engine??

175,000 miles on the old clock. I don't see an extension of the block that the sending unit threads into...looks to me like it just threads into the side of the block. Haven't given up yet, but still scratching my head. Thinking the engine mount may have to come out as holyford suggests...drat...and this is just to diagnose a suspected low oil pressure problem. Haven't gotten to the fix yet.

SD