I think it's achievable.
In addition for a sporty motor I would :
Use new ARP rod bolts & nuts.
Lighten, balance and straighten the conrods.
Rebore and use decent pistons- eg Russell Engineering or Hypatec.
Fit Mk2 S inlet valves, new exhausts, unleaded seats, and get the head gasflowed.
Lighten the flywheel.
Cracktest the crank before grinding (many 1275 ones are cracked).
Balance the crank, flywheel and clutch assembly.
Fit an orange dot clutch diaphragm.
Use a Maniflow medium bore LCB and RC40 exhaust.
Use a decent flowing intake system- single HIF44/HS6 on a good manifold, or a pair of HS4s, or a 45 Weber/45 Dellorto if you don't mind the noise.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.
