Hello tiger99!

This is every reel mower owner's worst nightmare. It's not uncommon.
There are two things working in your favour:

- the bottom block's captive washers may have given way.
- the machine offers reel protection via belt drive and springs.

In these cases, if the reel is not damaged, the most damage will be
the set has been compromised. Nothing more.

If there is damage to the bottom blade, then back-lapping may fix it.
What we need is for you to investigate the problem and supply us with
photographic information.

To answer your specific questions:
- the bottom blade is replaceable. Cost via ODK on-line store.
[NOTE: if bottom blade needs replacing a sharpen & set will be required]
- I do not believe the 45 and 430 reels are interchangeable.
- The reel can be re-shaped, but this depends on the damage encountered.

I hope this helps.
--------------------------------
JACK.