I couldn't agree more with Ashman. Have you ever done an engine swap? The engine itself might be inexpensive, but the conversion will not be. Then, once on the road you will most likely have numerous things to sort out. Been there, done that.
As far as your comments about MB, you happen to have one of the most complex of MB engines in the V8. These engines require close attention to timing chain and chain guides. If that is done, they are most reliable. I'm sorry that you have had bad luck.
There are reasons that the Small Block Jag is common. The first is that the Jag engines make the MB V8 you have, look very reliable and very inexpensive by comparison. Secondly, the Chev V8 configuration happens to nestle into the Jag engine compartment quite nicely; the oil pan sump in the right place and the dimensions fit well, etc.
Have a great day,