I've got some of those, and will start using a lot more, but the modern lenses are WR and a lot lighter, e.g. the choice for general walking and spotting wildlife:
Adaptall SP 60-300 + 1.7 AF converter + K-1 II = 2kg
Pentax 55-300m + 1.4 converter + K1-II = 1.5kg
Pentax DA* 300mm + 1.4 converter + K1-II = 2.4kg

So if I'm mainly walking, it tends to be the lighter, if I'm trying for best pictures, it's the 300mm. I'm looking forward to giving the Adaptall SP 300mm and 500mm some exercise as well.

For mid range I've got the Pentax A 50mm F1.7, Adaptall SP 90mm and Pentax 75-150mm, all really nice to use.

However I'm tending more towards picking up some primes at the wider end, and there it's much more likely to be old MF glass (my wide zooms are not WR). For now it's between the ultra wide ones (DA) and and FF old Vivitar 28mm and Tamron 28-105mm.

Mike

It was a K-1 II, was lucky to spot one at a good price.

The SD card slot is broken (hence being looked at for a second repair estimate), so can only use it tethered at the moment. The repair cost is about the same as buying another camera, so I took the plunge to FF instead.

When I can get hold of my K- 5 II (waiting for me to collect from the shop), I can let you have the grip terminal cover if it's the right part for the K3 as well.

Mike

I looked at those when my K5 broke, and was tempted, but then I saw a K-1 II for £1100 with 421 activations, and couldn't resist.

I've got a similar problem with my K5-II - but there is a visible pin out of line and it reports an error. I can use the camera tethered, so I know that's the only problem.

The quotes seem to be based on replacing the motherboard (which is expensive), but I'm considering dismantling myself, to see if I can replace the slot. I'm a bit nervous about tackling that, but otherwise it's a dead camera. Another option would be to find a camera that's got a mechanical failure, and get the local shop to do the work, which should be cheaper and safer.

Mike

Most of the time with the long lenses, I'm cropping anyway, so it's not too much extra work.

It is, but the 1.4x converter is not. The combination does provide good results, and I could use in crop mode, but there is a lot of extra sensor area that I can use as long as I'm prepared to crop later.

That's my plan, thinking about a good wide prime, but I want to experiment a bit to decide how wide.

I was using a K-5 II until a faulty SD card damaged the reader. A repair would have been as much as buying another, so I decided to make the move to FF. That means I've got the DA lenses that I will still use until I have time to find something better.

I've got some old glass that I will use as well, but a lot of gaps in coverage. The Adaptall 2 SP lenses are really good, but a little heavy for walking, where the 55-300mm is ideal, and I've nothing FF wider than 28mm.