Have you ever heard the saying. Pushing #### Up Hill. Cos thats what you are doing by not to pulingl the motor out. MLS has the best way to hold the cam followers in. But if you have to pull the sump off you have to undo the engine mounts so you may as well undo the dozen or so other things & pull the motor out. If you havent got the equptment to do that you can hire engine cranes or get some mates to help lift it out with a pole & chain & if you havent got a engine stand sit the motor on a couple of tyres & get a mate to hold it while you put the cam in. Its not hard man.

Get yourself a tub of petroleum jelly and put heaps on the lifter, that will hold them in place whilst fitting the cam.
The petroleum jelly will dissipate when you start the engine and get a little heat into it and not cause problems with blocking galleries or anything like that.
This is what had to be done to refit Renault 10 & 12 heads.

I guess that you could build a special brace that supports the engine in the car, then raise the car on a hoist, remove the inner suspension pivots, drop the crossmember out & remove the sump.
Then get four of your mates under the car to hold up the lifters while you slip the cam back in. Once it's back in, you need only put it all back together again.

I think that you will find that engine removal will be easier. It's all there in your workshop manual.

it doesn't matter if you can get the sump off with the engine in the car or not, because even if you retrieve the cam followers from the sump, you'll never get them and the cam back in with the engine in the car anyway - unless you have 8 telescopic magnets and an octopus to help out!

but can you get the sump off with the motor still in the enginebay or is the crossmember in the way

Thats the ONLY way to get to the lifters.

is it possible to get to the lifters if you remove the sump

that was my brothers method when he replaced the clucth in his sunny

If you can figure a way to hold the lifters up while you re-insert the cam, then go for it, but short of roling the car onto its roof, the engine will need to come out & this will be a lot easier than any alternate scheme that i have heard of so far.

everything you have listed has been done the cam is out and the lifters are in the sump. brought gaskets, cam lube, 2nd hand lifters and pushrods(old ones were bent and were making noises at 6000 rpm)

is there another way to put the new cam in