were would you buy them. how much more powerful is the LPR .28R spec 3 compared to the first two is it worth the cost. also will all the stock equipment also fit onto that engine including roto start.
Mach 28 is a dud, or so I've been told. The mach 26 is a dinosaur and I'd grab one of the newer mach's instead (427). But they can be hard to find. May want to hit ebay if your seeking one of those. The LST2 ran them as a stock engine as did the muggy, but they came with a roto start that won't work on a savage. You can find pullstarts for them for around $20 though.
As for the other engines, not sure about the roto-start on any of them, the mount/flywheel will fit without issue. You will more than likely need a new header gasket with any engine your purchase if it's been that long since you've had yours apart.
The LRP28S3 is a stump puller and fun, but can wreak havoc on the savage drive train. Same goes for the picco 28 as it's stronger than the LRP. You'd almost be better suited with a more mild Mach 427, green or gold head if your seeking durability and decent power.
This is losi's 454 which is a clone of the LRP28S3:
http://www.losipartshouse.com/servlet/the-29020/LOSR2200-Losi-454-Engine/Detail
LRP's new 30 that I believe is replacing the 28S3, more power and from what I've seen in vids and heard/read, it's peak RPM's are pretty close as well:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXXDA0&P=ML
At hobby people a bit cheaper:
http://www.hobbypeople.net/gallery/269503.asp
Here's the LRP28:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKYU8&P=ML
I have two of these. One in my savage and one in my aftershock. Both trucks are pretty highly modified for bashing, but the engine throws them around like a rag doll.
Picco 28:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXMCA4&P=ML
If you really want to go nuts, RB TM278:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXSLH7&P=ML
Never had one, but any RB I've heard in a vid, it sounds like it's seconds away from exploding, then you see the owner really hammer it and it just screams even more. A little to rich for this bashers blood though.
This would be a more budget minded engine, but should be a good one:
http://www.hobbypeople.net/gallery/146032.asp
I have an XTM 24.7 (which is about 2 steps down from that one) and it's a decent little engine. It's my savage winter engine.
Another budget engine:
https://www.ssl-stormerhobbies.com/cgi-bin/seekpart.pl?src=ns&pn=LOSR1001
Not awesome, but not bad either. Plenty of power for a typical savage basher.