*Disclaimer: bad idea ahead, read at your own risk.

Have an old Dodge D100 with a seized engine, but a really nice body. Have a lead on a v10 and transmission from a work truck for cheap. Could I drop them into that truck, or is it dimensionally not feasible?

Just guessing but I see some modifications in your future. Drop in? I seriously doubt it.

X2 but might be fun

Didn't expect it to be easy, but could it be done without completely revamping everything?

the v10 is really bad on fuel

X2

Really bad on fuel. Like 8mpg on a good day. A friend of mine had bought a dodge pickup with the V-10 when they were new. He only had it for about 1 1/2 years , then traded it in on another pickup. I asked him why. He told me he was averaging 6mpg.

Might be cheaper to get a shortblock and resurface the heads

I had a 95 v-10. Mine averaged 11mpg. Strong engine though, and very smooth. Lots of power and torque. From what I was told, which might not be correct, was that it is basically a 360 lengthened with two more cylinders. I don’t know if the means the mounting is the same.

I'd ask the pro's here!... https://moparforums.com/forums/f96/
and maybe here too:
http://dodgesweptline.org/phorum/list.php?2

kinda surprised ya don't already belong to 1 of them.
I find specific forums get me the most info, from the most experienced folks, in the shortest amt of time.
Like the F150ownersforum and chevy2500 and dodgecaravan and plymouthvolare and tahoeowners ........forums to get our vehicle info from, fast and experienced.

It's a novelty project, mostly to have a hillbilly hotrod.

I put a v-10 in an old big mopar car for a sleeper for a local hotrodder. Took a whole new firewall to make it happan. Take your tape measure and measure your length between your stock radiator and the firewall. If it's not at least 34-36 inches, your in for a zoo, pluss you will need a larger radiator to cool the big motor, width to accomodate it also. Plus the pan and oil pickup will have to be modified. Are your up for all of that? Then you have the wireing.....Have fun!

Seen a Honda S2000 once with a Viper engine in it , different engine than the V-10 in Dodge trucks. The guy called it a 'Sniper'

Crazy mod , tons and tons of work to get it to fit/run correctly.

That right there tells me all I needed to know.

A torch and a welder it’ll go in there.

Lol....and lots and lots of acetylene and welding rods....lol

Seen some weird mods in my day.
77? Camaro originally had a chevy straight 6 , put in a Chrysler slant 6
76? VW rabbit , engine relocated to the trunk , beer keg up front for a fuel cell
73? Plymouth Duster turned into a 4wd pickup
Late 50's Alfa Romeo with a 454cid chevy , drag car
93 Acura NSX with a LS6 Corvette swap , major job , years in the making
78? Chevy Monza with a 454cid chevy , not done too well , twisted whole car after a few burnouts until one of the rear wheels didn't touch the ground anymore.
And more.

Some strange stuff out there.......

My auto tech teacher always told us if you know how to do it and have the tools everything is easy, after every question that started with "how hard is it to...." I miss that guy

Beat it to fit, paint it to match. Done.

It should fit. I have an 83 d150 that I am pulling a 318 out of. Eagle hemi going to replace it

Put a 4bt in it, high 20s mpg and they run forever.