diff --git a/cardano-api/src/Cardano/Api.hs b/cardano-api/src/Cardano/Api.hs
index 9e9f8f04c1c..3cc0fe22c2c 100644
--- a/cardano-api/src/Cardano/Api.hs
+++ b/cardano-api/src/Cardano/Api.hs
@@ -67,6 +67,7 @@ module Cardano.Api (
     -- ** Byron addresses
     makeByronAddress,
     ByronKey,
+    ByronKeyLegacy,
 
     -- ** Shelley addresses
     makeShelleyAddress,
@@ -422,6 +423,7 @@ module Cardano.Api (
     -- ** Conversions
     --TODO: arrange not to export these
     toNetworkMagic,
+    toByronLovelace,
   ) where
 
 import           Cardano.Api.Typed
diff --git a/cardano-api/src/Cardano/Api/Byron.hs b/cardano-api/src/Cardano/Api/Byron.hs
index 22cd7ee0442..3cf3177c308 100644
--- a/cardano-api/src/Cardano/Api/Byron.hs
+++ b/cardano-api/src/Cardano/Api/Byron.hs
@@ -81,9 +81,12 @@ module Cardano.Api.Byron
     toByronLedgertoByronVote,
 
     -- ** Conversions
+    fromByronTxIn,
     toByronNetworkMagic,
     toByronProtocolMagicId,
     toByronRequiresNetworkMagic,
+
+    makeByronTransaction,
   ) where
 
 import           Cardano.Api
diff --git a/cardano-api/src/Cardano/Api/Tx.hs b/cardano-api/src/Cardano/Api/Tx.hs
index 024ffa0dbe5..f218f0f07fe 100644
--- a/cardano-api/src/Cardano/Api/Tx.hs
+++ b/cardano-api/src/Cardano/Api/Tx.hs
@@ -73,11 +73,11 @@ import qualified Cardano.Crypto.Wallet as Crypto.HD
 --
 -- Byron imports
 --
+import qualified Cardano.Chain.Common as Byron
+import qualified Cardano.Chain.UTxO as Byron
 import qualified Cardano.Crypto.Hashing as Byron
 import qualified Cardano.Crypto.ProtocolMagic as Byron
 import qualified Cardano.Crypto.Signing as Byron
-import qualified Cardano.Chain.Common as Byron
-import qualified Cardano.Chain.UTxO as Byron
 
 --
 -- Shelley imports
@@ -521,9 +521,10 @@ makeSignedTransaction witnesses (ShelleyTxBody era txbody txmetadata) =
           (maybeToStrictMaybe txmetadata)
 
 
-makeByronKeyWitness :: NetworkId
+makeByronKeyWitness :: forall key. IsByronLegacyFormat key
+                    => NetworkId
                     -> TxBody ByronEra
-                    -> SigningKey ByronKey
+                    -> SigningKey key
                     -> Witness ByronEra
 makeByronKeyWitness _ (ShelleyTxBody era _ _) = case era of {}
 makeByronKeyWitness nw (ByronTxBody txbody) =
@@ -535,11 +536,18 @@ makeByronKeyWitness nw (ByronTxBody txbody) =
 
         -- To allow sharing of the txhash computation across many signatures we
         -- define and share the txhash outside the lambda for the signing key:
-     in \(ByronSigningKey sk) ->
-        ByronKeyWitness $
-          Byron.VKWitness
-            (Byron.toVerification sk)
-            (Byron.sign pm Byron.SignTx sk (Byron.TxSigData txhash))
+     in case isLegacyFormat :: ByronKeyFormat key of
+          ByronLegacyKeyFormat ->
+            \(ByronSigningKeyLegacy sk) -> witness sk pm txhash
+          ByronNonLegacyKeyFormat ->
+            \(ByronSigningKey sk) -> witness sk pm txhash
+ where
+   witness :: Byron.SigningKey -> Byron.ProtocolMagicId -> Byron.Hash Byron.Tx -> Witness ByronEra
+   witness sk pm txHash =
+     ByronKeyWitness $
+       Byron.VKWitness
+         (Byron.toVerification sk)
+         (Byron.sign pm Byron.SignTx sk (Byron.TxSigData txHash))
 
 -- | Either a network ID or a Byron address to be used in constructing a
 -- Shelley bootstrap witness.
diff --git a/cardano-api/src/Cardano/Api/TxBody.hs b/cardano-api/src/Cardano/Api/TxBody.hs
index 52ab7f9031c..56638c76ff9 100644
--- a/cardano-api/src/Cardano/Api/TxBody.hs
+++ b/cardano-api/src/Cardano/Api/TxBody.hs
@@ -86,6 +86,9 @@ module Cardano.Api.TxBody (
 
     -- * Data family instances
     AsType(AsTxId, AsTxBody, AsByronTxBody, AsShelleyTxBody),
+
+    -- * Conversion functions
+    fromByronTxIn,
   ) where
 
 import           Prelude
@@ -224,6 +227,13 @@ newtype TxIx = TxIx Word
   deriving stock (Eq, Ord, Show)
   deriving newtype (Enum)
 
+fromByronTxIn :: Byron.TxIn -> TxIn
+fromByronTxIn (Byron.TxInUtxo txId index) =
+  let shortBs = Byron.abstractHashToShort txId
+      mApiHash = Crypto.hashFromBytesShort shortBs
+  in case mApiHash of
+       Just apiHash -> TxIn (TxId apiHash) (TxIx . fromIntegral $ toInteger index)
+       Nothing -> error $ "Error converting Byron era TxId: " <> show txId
 
 toByronTxIn :: TxIn -> Byron.TxIn
 toByronTxIn (TxIn txid (TxIx txix)) =
diff --git a/cardano-api/src/Cardano/Api/Typed.hs b/cardano-api/src/Cardano/Api/Typed.hs
index ee953552099..e88ee5ff096 100644
--- a/cardano-api/src/Cardano/Api/Typed.hs
+++ b/cardano-api/src/Cardano/Api/Typed.hs
@@ -84,6 +84,8 @@ module Cardano.Api.Typed (
     -- ** Byron addresses
     makeByronAddress,
     ByronKey,
+    ByronKeyLegacy,
+
     -- ** Shelley addresses
     makeShelleyAddress,
     PaymentCredential(..),
@@ -475,6 +477,8 @@ module Cardano.Api.Typed (
 
     -- ** Conversions
     --TODO: arrange not to export these
+    fromByronTxIn,
+    toByronLovelace,
     toByronNetworkMagic,
     toByronProtocolMagicId,
     toByronRequiresNetworkMagic,