I am considering installing 4.5L and trans from a 1978 R107 to replace my failing M130 in a 1971 W114. From the threads I have seen numerous comments that this may be possible due to common subframes. I do not want install any Detroit small block engines, but would like to have the smooth power I found in my Dad's 450 sedan.
Any good comments will be appriciated.

My suggestion would be to find an earlier 4.5, like 71-72, as these would be typically higher-compression (and not the smogged 4.5s that have lower output). Barring that, I'd go straight to a 500 or 560 engine from the 107 before a 78. The reason being they'll be lighter and still give more power than the smogged 4.5 would. You can put a 108/109 3.5 or 4.5 in but you'll likely need to swap the oil pan & oil filter mounts from a 107-chassis V8.

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Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

The W114/115 engine room structural sheet metal is much narrower than the R107 or W108 or W116 or W126. The 114/115 chassis was never intended to house a V engine. There are considerable interference problems, the most notable of which involve steering components, specifically the steering box and/or idler arm mounting locations. The only possible, viable V engine installations would seem to be the use of a 60 degree V6 with the starter motor on the right side. The 60 deg. configuration can place the starter high enough above the crankshaft centerline to clear the steering idler.

I know you don't want to do this, but had to share the link: LS1 Swap into 75 280 W114 Starts Tomorrow - Benzworld.org - Mercedes-Benz Discussion Forum

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Looking for Early 108 windshield surround wood in decent-to-good condition.

the M110 six is a smooth power maker, when all the smog **** is ripped off, it makes decent power and can breathe better then the M130 as it's DOHC.

you'd run into issues with the Differential being geared too low for the M117. not to mention if you swap a D-jet engine you need the whole harness or megasquirt. and the transmission tunnel may have to be cut larger.

I'd up the compression of the M130 and play with the timing before I'd swap motors.

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R107.043 Euro 350SL (parts)(crushed)
W116.024 280se (crushed)
W114 280 (m110)
W108.067 280se 4.5
W108.068 280seL 4.5 (crushed)
W111 220SEB coupe
W110 200D went to the crusher
W110 190D sold sold sold

1970 Rover P6B

Used to own(1950 buick,1969 lincoln MK3,4G63t colt,87 300ZX, 79 F100, 92 XJ40)